I was just going to mention this, but with more detailing.... Could this possibly mean.... ISAAC?! Oh god the possibilites
Aside from Mewtwo (the obvious one), no other character should really be expected to come out before the remaining vBrawl characters. Mewtwo is in the process of coding, has had some work put into him, is quite iconic and there's a reference (Melee), so things are under-way and he could very well show up before someone like Ice Climbers/Yoshi/Kirby are finished up since they involve so much work in themselves, and technical issues, whatever (I don't know the details of this) that could potentially make them as much work as Mewtwo even.
Otherwise, if anyone is to be added, it will likely be one of 2 things, and also 'should' be one of these 2 things.
1) Something simple, functional, fairly modernly known and established. Possibly as a long-term project used as a base for developing things further regarding things that HAVE NO REFERENCE. A character that has a lot of content to work with, and wouldn't be overly debated in terms of HOW they work were they included.
Example: Bowser Jr. with a Squirtle direction and Bowser base, or vice versa. As simple as it gets in terms of the work (still a lot) with references (other games, but nothing complex) and bases (options and images galore from in-game), but still remaining very unique in the roster, giving him a PURPOSE to be there.
2) Something iconic, nostalgic to some, fairly niche and to the extreme as 'unexpected' as an inclusion, but only due to the way a project like this would really be over the top, and a lot of specifics and detailing would be need to make it happen. A character that would have a lot of details as far as HOW they work in the game.
Example: Isaac. which would have very little to work from in terms of particles, details, and anything in terms of reference for how it would work in Smash, and likely be tampered to be very stand-out in the cast with PURPOSE, because something this dramatically challenging to the game should be. This would be going all out.
Those are the extremes of it, and neither should really be tampered with until after Mewtwo + full vanilla roster, unless people are too crazy good and go hard on this stuff, which I wouldn't be 'too' surprised, but it's unreasonable to expect. There are some crazy people out there though.