13-18 newcomers? I wouldn't count on it. I seriously believe we'll see no more than 10-12 excluding third party and transformations.
When I was talking about running out of characters, I'm talking about how we're on a limited "resource." When the well runs dry, if it should, what we will do for new characters?
I have always talked about the "well running dry", but not much about what will happen when it finally does. First off, its very difficult getting a fighting game to have more than 50 characters. Most of the time they do get over 50, it is either due to much of the characrers being clones or rips from previous games of the series utilizing a similar engine.
Since Smash games are once on a console deal, the engine has to be made alongside the characters. Simply because the moveset is already made out does not mean that they will simply mean they can simply make Smash 4 and copy and paste Brawl's characters into the game.
I think Sakurai's team was able to do what they did partially because the Wii is extremely similar to GameCube hardware. Most of Nintendo's teams will be a generation behind when Nintendo does decide to make a new console with similar graphical power compared to the Playstation 3 and X-Box 360.
I do think we will probably see around 45-55 total playable characters in Smash 4. The number of newcomers really depends upon how many characters in Brawl's roster that they decide to cut. Remember while the size of the Brawl roster increased by 13 characters over Melee, that Brawl had 18 newcomers.
There are much less "obvious" cuts in Brawl as there was for Melee. The only ones that seem like cutting material are Pokemon Trainer (if only for the number of characters his slot takes up), Lucario, Ike, Lucas, Toon Link, Wolf, Sonic, Snake, and R.O.B. (who interestingly was the only character from Mario Kart DS not to return for Mario Kart Wii). Most of the previously mentioned characters have much more popularity than most of the cut Melee veterans (the only two cut Melee characters whom had a sizable fanbase were Mewtwo and Roy, and maybe Dr. Mario had some fans).
Here is my reasoning behind each of the listed:
Pokemon Trainer:
Some complain about too much 1st-generation playable representation. Also, Pokemon Trainer's slot takes up three characters, and the character itself is less popular than the flavor of the month Lucario.
Lucario:
Many believe him to be an advertisement for Pokemon Diamond/Pearl. Many also prefer Mewtwo over Lucario. Overall, Lucario is indeed a flavor-of-the-month Pokemon, and his staying power has eroded in the Smash fanbase and his popularity has fallen behind even other Smash mainstays such as Pikachu and Jigglypuff, and even the cut Mewtwo (this is talking about Pokemon popularity in Japan). Lucario's biggest problem is Sakurai not looking at Zoroark to be a replacement to him. However, Lucario does benefit for being releatively popular among competivie players, and overall a much more popular Pokemon newcomer than Pokemon Trainer.
Ike:
Another "flavor-of-the-month" character. Ike's story in Fire Emblem is finished., and due to the recent release of his games, they likely won't be remade any time soon. Ike has lots of popularity among casual Smash players though, and an unique moveset. He is also relatively well-liked by Fire Emblem fans. Ike's chances of returning depends on whether Sakurai thinks Fire Emblem deserves three characters, and whether Ike has outstayed his welcome by the time Smash 4 begins development.
Toon Link:
Unlike most of the characters listed here, Toon Link has seen a new release since Brawl. Spirit Tracks did sell well, and perhaps we will continue to see cell-shaded Zeldas on Nintendo's next handheld. Toon Link's biggest problem is that he is easily the cloniest of Brawl's clones. Toon Link is very much a Melee styled clone, whereas Lucas and Wolf both had different A-moves and throws. Toon Link is the only Zelda character that is liked among competitive players though.
Wolf:
Wolf was either the last or second-to-last addition made to Brawl's roster. Wolf is liked among the casual fans of Smash Bros., however, there are some who felt that a certain other Star Fox character should have been in. Many felt that three Star Fox characters was already too much, and that four would be ridiculous for a relatively small series such as Star Fox. Wolf's biggest danger is that Sakurai does think about matters of series having too many characters (he addressed this in a Nintendo Power interview when asked why Mario and Zelda did not see any more characters compared to Melee). If the Krystal fans are loud enough for him to think she is a worthy addition, and if Sakurai deems that Star Fox should not have four characters, Wolf may face the chopping block.
R.O.B.:
Probably the least popular character on Brawl's roster. He was the only newcomer that I saw as much outrage for inclusion that I did for Dr. Mario, Pichu, and Young Link. However, R.O.B. benefit from having an unique moveset, and he did not cut out the equally obscure retros from Melee. However, keep in mind that R.O.B. was one of the few Mario Kart veterans to not have been included in Mario Kart Wii...
Lucas:
While there are a few that think Mother should have as many characters as Mario, most are relatively happy that Mother even got a second character. Itoi, the creator of the Mother series, has repeatedly said that he is done with the series and Mother 3 did not end with a cliffhanger like the first two did. Moreover, two of the three games in the Mother series are Japan-only. Lucas is also the only Japan-only character on Brawl's roster. In many ways, I felt Lucas's inclusion was to honor that Mother 3 finally did get released. However, as from Melee to Brawl, Sakurai's feelings about him being a worthy inclusion could also change. Ness's seniority protects him compared to Lucas, and if pressed for space on a limited roster, cutting Lucas might be deemed "no big deal" by Sakurai's team.
Sonic:
Sonic was either the last or second-to-last character added to Brawl's roster. Sonic also is said by many Smash fans to have had one of the most bland movesets of Brawl's newcomers. While Sonic is quite popular among casual fans, Sonic is a rather poor tourney character. Sonic as a playable character, does not add much. However, in Sonic's favor, lots of Sonic games have been made for Nintendo consoles following Brawl's release, and even some mediocre sports crossovers with Mario. However, Sonic's games continue to be in the sub-par territory, and while many look fondly on his Genesis/MegaDrive days, he is largely looked up as being a "has-been." Also, we do not know Sakurai's policy regarding "guests", do "guests" only stay for "one night" (one game) as is the case for many other fighting series? Or will Sonic become a permanent staple for Smash? Perhaps, Sakurai might feel new guests are needed to distinguish Smash 4 from Brawl, or even that "guests" ruin what Smash is about. Regardless, most of Sonic's popularity is among casual Western fans. On Japanese tier lists, Sonic is regarded as being one of the worst characters in the games, and the Sonic games in Japan have sold very poorly in recent years.
Snake:
Snake was the first guest character of Smash Bros. Snake largely got in due to Sakurai and Kojima being close friends. However, it seems that despite Snake's inclusion in Smash, there has been no new Metal Gear games for Nintendo consoles. The Nintendo DS, the highest selling game console of ALL TIME, received no Metal Gear games, whereas the PSP received four. The Wii has also not received any Metal Gear games (outside of the Virtual Console), while the Playstation 3 has received two and the X-Box 360 is getting one. Snake does offer an extremely unique moveset though, and is popular among both casual and competitive Smash players. However, Snake's problem is that his main reason for inclusion was a personal tie between the creators of Smash and Metal Gear, and outside of that, Metal Gear has little to do with Nintendo. Snake, has been in Smash, so Sakurai's favor to Kojima has been fulfilled, so Kojima might feel that since Snake has already taken on Nintendo, it might not be necessary to come back for "round 2". Again, it largely depends on Sakurai's belief about "guests".
Wow, its been a long time since I last typed this much for a post on this forum. I am sure a lot of you will find this post intriguing and interesting, while some will also find it objectionable. Regardless, I hope it was a worthy contribution to this topic at hand. I still think its too early to make reasonable roster guesses, and that Smash 4 does not really have any "shoe-ins" that Melee and Brawl had.