My theory is that they will have 4 new characters in the Wii version.
Because of the trophies in the game I think they will be
1.Roy
2.Ridley
3.Snake
4.Isaac
These 4 are surprising and seem unlikely but how can they not get acknowledged at all? Especially since 2 of them are veterans.
I think Snake has too unique of a move set not to be in and Roy would blow everyone's mind.
Just my theory. Later down the road DLC for Wii version and a newer version for the new 3ds that can support ice climbers, ect.
Likely the New 3DS version is getting nothing special in terms of playable characters. Old 3DS players can't be left out. It's a very fickle situation at this point. The best thing to do is give the 3DS cartridge and Wii U disc the exact same playable characters. Remember, if you can only get the characters on the New 3DS system, you leave earlier system owners out. Thus, you get pissed off fans. So keeping the rosters the same based upon the literal game and not the playable system succeeds in leaving no one out).
As for your list, I'm not so sure on some of them. He teased Ridley, so we at least know he is possible. Isaac is just in an odd placement. People wanted him, but Dark Dawn really bad reputation may make him less likely. He may still be an AT. Snake requires a lot of money, and we don't know if he can get him back. Konami and Nintendo aren't on good terms. This is likely why he was cut. It's quite possible he was originally coded in, but then removed due to executive meddling.(don't take the Fox Weekly article as more than a grain of salt. The site isn't the most credible, even if it's unrelated to Fox News, and an anonymous source is highly suspicious. Likewise, Sakurai might not be able to explain Snake's cut if it's executive meddling. That'd be basically dissing Nintendo, who he works for. He can't say bad stuff about them and all.) Roy has one issue. The other Roy. They have to recode the game so his name shows up as Roy Koopa as is. Likewise, let's say that Roy(Koopa) has the file names of Roy in the coding. Rewriting all of that just to add a guy with the same name isn't that easy. Sure, our firey guy is possible, but he'd have a new code name(Roy's was Fire_Emblem in Melee, notably) for every related file. It's not impossible, but they have to figure out if it's worth having two characters be announced by the announcer with the exact same name. Do they record new files? Do they re-use it by copying the file under a different name? Not that I don't want Roy back, but he's not that likely due to the work needed to be done.
There's a lot of miligating factors to take into account. We can all want these guys. But nothing's ever easy. I still think Ridley has the highest chance(at least if his Wii U role isn't a very complex stage hazard. If it is, his chances lower by default. If he has little programming, Sakurai can easily do another version of him. If he has very complex programming, he most likely only wanted him in that role. However, that may not matter either way, but that's just a plausible theory. If Ridley is a very complex stage hazard, he'd be the first one ever. That's why Sakurai teased him. That's why he wouldn't tell us a thing about him. He's a very special and unique programming idea. It's logical. I'm sure more think "playable" is a better thing to tease, but he may not see it the same, along with Mewtwo, and maybe a revamped Wolf/Lucas/Pichu. Mewtwo is highly popular. And to be fair, GameFreak may be why he's not in as well. As noted above, they tend to have some control over the choices. Sakurai outright works with them, for better or worse. Pichu has the same issue, but he's faster to make due to still being a clone, but can be updated with better moves, and maybe luigified a bit. He's no good as an alt solely because he hurts himself. Wolf is easy. Just remake him from Brawl with some balancing ideas based upon his build when they test. Lucas could play like his Brawl self with ease. He'd be different from Ness even in 4.(to note, Ness stole his B moves, and some of his A moves were changed up to be a combination of them).
It's a lot to read, but it's all worth noting. The one last thing to say is that if Sakurai wants someone playable for DLC, you might as well expect them in bar technical issues like the IC's(who are probably gone from 4(3DS and Wii U cartridge and disc respectively) for good unless he can fix those), or executive meddling from the creators of the characters, which I don't think is an issue for Ridley anyway, but could be for 3rd parties(I.E. Snake).