Toon Link - 75%
No doubt, TL has to be one of the most likely Brawl veterans to be cut. Let it be a vote of confidence for the Brawl roster then that I think even he's got a stronger chance of returning than not. The way I see it, he has three big strengths going for him:
1. He appears in more new Zelda games in the last decade than normal Link. No, really! Since Wind Waker in late '02, we've had four other games with Toon Link (FSA, MC, PH, ST) and just two with other incarnations of Link (TP, SS). Even if you include OoT3D and Crossbow Training they're only tied, and WW HD and ALBW will maintain the tie. Simply put, Toon Link is a big deal in modern Zelda!
2. Counting Young Link as his spiritual predecessor, we've had two Smash games with a small, quick Link in them. As such, it wouldn't be surprising to find that Sakurai wants to continue that legacy, and unless you really want to argue Classic Link is small enough and more unique than Toon Link, there's no other Link better for the job.
3. There really isn't a serious contender for the fourth Zelda slot, assuming Zelda doesn't lose one altogether. Impa and Tingle lack popularity, Ghirahim is just the latest in a long line of one-off villains, Vaati is recurring but hasn't appeared since Minish Cap in '04, and Toon Zelda/Sheik/Tetra already lost out to Toon Link back in Brawl. Seems to me Sakurai's more likely to simply keep Toon Link than pick a lesser character.
There are those that think he's doomed as the cloniest clone in all of cloneville. While true, it's still a clone archetype that has seen two games and could easily be decloned using the diverse Zelda arsenal if desired. Others will point out that he appears on the Spirit Tracks stage. It's true the Spirit Tracks incarnation of Toon Link does appear there, that hasn't exactly stopped the Blue Falcon from racing on the F-Zero stages, nor has it stopped retro Donkey Kong from appearing at the top of 75m, never mind that the Toon Link from Brawl is based on Wind Waker, not ST. Then there are those that simply cut him because he's another Link, and who needs two Links? Well, Sakurai apparently has...twice.
Could Toon Link be cut? Sure, it's possible. That said, I don't think he's the longshot others seem to think. Seems like a pretty strong contender to me!
Want - 100% - I mained him in Brawl, and while I have yet to carry over my main between Smash games, that sure won't stop me from trying if TL is still in SSB4.
Mewtwo Prediction - 78.5%
He's going to get a lot of high ratings from both sites. I'm not sure he'll see any serious detractors aside from the fact he's been cut before.
Nominations
5x Lucina