It's tough to decide this kind of stuff. Nintendo always gives us what we don't expect, gotta get some pictures to make this easier.
Anyway for me I predict for newcomers: Mewtwo, Paper Mario, Lil Mac, Mii's, Ridley, Chrom, Paluatina.
My comments:
King K Rool would be nice, but I'm not too sure about that one.
I don't know much about Crom, but I think they'll put him in, seeing what they did with Roy and Ike.
Mii's, as much as I don't like this, I'm pretty sure it will happen.
Ridley, have any of you watched the Shokio video? Ridley really isn't that big, it can easily be downsized, you can still make it pretty big anyway, just not like "boss" big.
Mewtwo is self explanatory.
I'm new here, but some of these seem very unrealistic, I don't think Nintendo would add some of this stuff, but hey, expect the unexpected!