Probably with my calculations we will have the Smash with the most new comers from a new series only behind Smash 64. If my predictions are correct here is how it should work.
Smash 64: 12 characters / 10 series
Melee: +14 characters = 26 characters, no cuts = 26 characters / + 3 new series = 13 series.
Brawl: +17 characters = 43 characters, 4 cuts = 39 characters / + 6 new series (2 third party) = 19 series.
Smash WiiU/3DS: + 14 characters = 53 characters, 3 cuts = 50 characters / + 8 new series (2 third party) = 26 series.
My reasoning for this math is the follow, we know from a Interview that Sakurai said that the new Smash will have less new characters than Brawl, if we see the pattern in Smash 64 we have 12 characters, then in Melee we have 14 new characters and finally in Brawl we have 17 new characters so if we sum all the three and take the average out it will be 14.333 in other words 14 now if we take this number in context is not farfetched comparing to what Sakurai said about having less new comers that in previous installment and comparing it to Melee in fact are in with the same number so we know that at least Sakurai this time can work really comfortable with this number from the previous games and how they work it out and now considering that they don't need to make so huge work in a Sub Space Emissary Mode the team will have enough time in working this out.
Now here is the second part if we add +14 characters the number would be 53 that is really a huge number of playable characters, now from the previous interviews to Sakurai he say that probably we will have some cuts it will be minor and he will try to no make cuts but it will happen and I prefer to think in that way sometimes you need to make cuts to progress the game with new playable characters or cut the things that do not work at all (there is no need to work something out if you know from start that it will not work out). Now that we know from the previews interviews that Sakurai will work out most of the characters for example from Melee to Brawl were 4 cuts (I´m not taking in consideration Young Link and Toon Link in this equation because I think this case has special condition where Toon Link is the spiritual successor and dosen't need to count especially when Sakurai did mention that he always keep two Links, one young and the other more mature because it represents the both sides of the same character) well we know that we will have cuts but they will be less a nice number will be 3 cuts making the roster with 50 playable characters that for a fighting game is huge and we need to take in consideration that some of the veterans are having a huge revamp in their movesets because they didn't work so well in the previews games.
Third point we know now that there will be 50 playable characters, that from the previews 39 characters in Brawl we will get 36 to open more spaces and development in a better roster following this now we are going with the new series if we go by numbers we will see that in Melee there were 3 new series, that in Brawl we get 6 new series with two of them being third party if we continue with this pattern we will have 8 new series with 2 new third parties in it and here is my reasoning.
We know of at least two new comers that are Villager and WFT, and we know of the first third new party that is Mega Man. now this is where rumors leaks, cameos, predictions comes to play, we have seen the boxing ring that is obviously a stage from a important character that in the previews Smash was an assist trophy and his name is Little Mac not only that we know that a leak did mention that the newcomers will be Villager, WFT, Mega Man, Little Mac, Miis and Pac-Man. Seeing this pattern we could get the follow list.
6 new series:
-) Villager (Animal Crossing).
-) Wii Fit Trainer (WFT).
-) Little Mac (Punch Out!).
-) Miis (Wii Sports Series and Avatar of the new consoles).
-) Mega Man (New Third party).
-) Pac Man (New Third party).
We have six for now but if we follow the pattern of Sakurai and how he works with Smash we can conclude that there will be two more series in that list and that would be the Retro Character that in previews games he show, in Melee it would be the Ice Cilmbers and in Brawl would be Pit. So we need to add Retro rep to the list above.
7 new series:
-) Villager (Animal Crossing).
-) Wii Fit Trainer (WFT).
-) Little Mac (Punch Out!).
-) Miis (Wii Sports Series and Avatar of the new consoles).
-) Mega Man (New Third party).
-) Pac Man (New Third party).
-) "Retro Rep" (The runners for this spot will be Takamaru, Mach Rider, Lip, etc.).
Now we need to think in the last two games we did get another idea of what we can expect from Sakurai and that are now what I call them the Historic Characters, for Melee was Mr. G&W and for Brawl was R.O.B. (both are very important to the success of Nintendo one was the first Handheld from Nintendo and the introduction to a bigger business in the videogame world and the second was the introduction to a Foreign market that was previously dead, the American market and with success that got it was a new era for Nintendo). So we have two Historic characters following this pattern we can expect a new one in the new Smash, so now our list will be like this.
8 new series:
-) Villager (Animal Crossing).
-) Wii Fit Trainer (WFT).
-) Little Mac (Punch Out!).
-) Miis (Wii Sports Series and Avatar of the new consoles).
-) Mega Man (New Third party).
-) Pac Man (New Third party).
-) "Retro Rep" (The runners for this spot will be Takamaru, Mach Rider, Lip, etc.).
-) "Historic Rep" (This character I don't have idea maybe Daitoryo character that is the character from the Hanafuda cards, or maybe Diskun that was the character from the Famicom System or even a Virtual Boy rep that can represent that console, is a wild card for me).
Now we have our 8 new series if you rest the 14 new characters you will have 6 new comers from the previews series making it to Smash, this new game will be the one with the most new series introducing new characters since the first one (not bad for me, this time Sakurai is focusing more in the introduction of new series to Smash that will help to inject new blood to an old Series).
If you ask me who will be the new 6 comers to the preview series it will be the follow:
6 new characters from the previews series:
-) King K. Rool or Dixie Kong (I don´t know who Sakurai will choose, both have good chances and will be a really hard competition).
-) Ridley (It has a big following in the west and Sakurai is trolling right now with the Pyrosphere stage in which appear Ridley, not only that Metroid at least need one more Rep).
-) Palutena (Sakurai did make the new Icarus game, the game did pretty well and was well received in general, not only that if I remember correctly Sakurai did want that most of the series could get a even participation in the playable characters).
-) Chrom or Roy (a new rep from Fire Emblem is coming who will it be I think the competition is between Chrom and Roy again is a gamble who will be the character).
-) Mewtwo (the most wanted character from Melee and with the huge success and popularity that has now I don´t think we should worry with which Pokemon we will get this time).
-) Porky (My biggest gamble is this one, could we get a new EarthBound character I don´t know, is this one or getting a new F-Zero Rep but following the love that Sakurai has for this series probably I will bet on this).
Now finally who will be my three cuts: Falco, Lucario and Lucas, my reasonings are the following, Star Fox has a problem that the three characters have almost the same concept of gameplay in them and almost look identical making it seem that we can cut one of them and we will not lost to much especially when the series is going with a long hiatus if Sakurai needs to cut someone probably will be Falco or Wolf (and seeing that Wolf has better reception and Sakurai likes more the character we can predict who will get the axe).
Lucario, my prediction is that it will be a Pokemon, in the transition between Melee to Brawl we lost two reps from Pokemon and we win two completely new Reps making the series with the most changes from one game to another so if we follow this pattern at least we know that one Pokemon rep will get the axe to get the inclusion of Mewtwo, and now my thinking in why Lucario. I know both characters dosen't have the same movesets and their playstyle is completely different but if I need to say something is that Lucario for me is like Mewtwo 2.0, Sakurai did want to change the character and make a revamp of say character but with a new look so probably the fans will not rage for the new gameplay of say character, but now that Mewtwo is back maybe we will get Mewtwo 3.0 where he gets the better of Melee and the better of Lucario to mix it in one character and finally get a decent moveset (lets be honest neither of those characters in the past have a great gameplay and most of the people did say that Lucario should be revamped asap and Mewtwo too).
Lucas if we follow the pattern Sakurai replace one character of their series with another one and didn´t get a series under cut (the exception was Mario series with Dr. Mario but I think is a especial case), lets take a look to the Pokemon situation (cut Pichu and Mewtwo and replace both with Pokemon Trainer (3 in 1) and Lucario) and Fire Emblem (replacing Roy with Ike) if we follow this pattern Lucas was well received but finally didn´t make it big and still has problems the same did happen with Ness. For me this is where I a gamble in favor of cutting Lucas because Sakurai could cut Ness (he almost did it in Brawl) but finally Ness has seniority (is one of the original 12) so the best that can happen with Ness is to receive the best of Lucas and try to add it to the character not only will it revamp the character but it can make him better, now we have talk patterns and if one of those characters get the axe the series will have one character to represent their series is not bad but Sakurai loves this series to much to cut one rep and have only one rep from that series so he will replace it with another one and here is my gamble could it be Ninten or Jeff or Porky (I´m choosing Porky, he is the main villain of the series if we think about it and he is the character that appear more in general not only that his moveset could be pretty unique and he did appear as a boss in Brawl, so probably will be in the same context as Ridley was in Brawl) is still a big gamble.
Ughh... it was a long theory, I hope someone read this and can tell me her or his opinion of this.