There are a couple shoe ins still left to announce...
Then of course...
and (sighs), probably Jigglypuff
I just don't see them leaving out any originals, but I'm sure Nintendo is begrudgingly adding them since Falcon and Ness haven't had an individual game in forever. Jigglypuff is unfortunately still pretty popular in Pokemon and gets play in Smash.
I'd expect maybe one more big third party reveal for E3, but I don't know who that could be. Sonic and Mega Man were the #1 and #2 most requested. Tails? Snake? Rayman? Dr. Eggman? Simon Belmont? Pac-Man?...who knows.
I think Krystal still has a good shot since there is only one Star Fox rep right now, it would be another female, and because Namco did create her and are developing this new Smash. I think Metaknight will return for similar reasons (Sakurai). I can't see them overlooking Xenoblade, so Shulk could be in. Maybe Palutena? Or Ghirahim?