One question I've been pondering over is: Just what will Nintendo have to do to get the game to sell like mad (at least in their minds) if it's a deluxe addition of Smash Wii U? I mean, when you think about it, even if all they did was a balance patch, many of us would likely buy the game all over again just to keep up with the standard, and then there would be all the Switch owners who had no interest in Wii U and never owned the game in the first place... At the same time, I can't imagine Nintendo NOT adding anything, though that would be the ideal expectation since Smash dream additions/changes often cause some pretty strong emotions when they're not fulfilled. LOL
It seems to me, if they want to max out sales for a deluxe addition to the greatest degree possible, adding at least a couple new fighters would be the logical thing to do (they did that much for Mario Kart). The couple of past reliable sources who have hinted or even flat out said there will be new characters have mentioned there being at least two, and if my memory isn't deceiving me, I believe some of those sources were even originally led to believe this deluxe Smash would release with the Switch, later changing to a six month release window from the launch of the Switch... If this is all true, it would imply something is definitely being worked on to make Smash take a little longer to show up. So, if we take the word "new" to mean non-veteran, which two new characters would bring in the most cash?
Most of us would probably agree on Inklings being one of them, at least from Nintendo's side of things. Splatoon is current and a strong IP, and the Inklings should have no trouble fitting in with the Smash world, especially considering some of the characters we already have. If the second character were to come from Nintendo, then options open up because of so many factors, I really wouldn't even be able to guess who it could wind up being. Would they go with a highly requested fan favourite like Isaac (not saying he's the most requested, just an example), an oddball blast from the past, maybe a character from TLoZ:BotW to keep with current interests, or even pull a Corrin and reveal someone from an upcoming title? It's honestly pretty difficult to figure out what will stand out and grab consumers sometimes, let alone what Nintendo thinks will...
If one of the two came from a third party, I guess the most relevant addition would be Bomberman at this point since he is current, a blast from the past, and widely recognizable. Then again, they've pulled wild cards on us like Cloud, so this is pretty tough too... If Snake actually has a chance, and we only received two characters at the most, he could potentially even take the place of a newcomer due to his popularity and the attention anything Metal Gear related automatically brings. Which character would sell the most copies, Bomberman or Snake? Hmmm...
I won't be surprised if at least one veteran makes it back. Ice Climbers seem to depend on the technical capabilities of the system, though I think that's pretty funny since 4-player IC lag didn't hold them back from getting into Melee and Brawl (was pretty easy to make the frames drop), but then frame rate is a bigger concern to today's gamers. Not sure who has the biggest following, Ice Climbers or Wolf? In my case, I seem to see more concern over ICs on Twitter and such, but seemingly more in Wolf's favour among the more dedicated Smash community.
Of course, if there ended up being DLC, all of this could change around. Maybe a deluxe version would just come with all past DLC along with further balancing (again, I can't really see this being the vanilla release, but I guess it's possible), but then add exciting content into the mix some time after release.
To briefly touch on costumes, I can't understand where Nintendo's thinking is on this. Numerous people keep mentioning how simple it seems to be for modders to make new fighter skins, yet the developers who understand the game's workings better than any of us never decided to take advantage of the obvious interest there outside of Miis. They have to be aware of all the modding going on, so will they finally take advantage of the money to be made on costumes alone? It's not like Sakurai would be required for direct input on this, but still, Nintendo is just so hard to figure out...