I doubt Ness is coming back, simply due to the fact that Lucas's move-set is extremely similar to Ness's move-set from Melee. If Ness does come back, I'm betting on an alternate costume, or just a new move-set.

As for Marth, well, he rocks, and it seems like the only move of Marth's that Ike really shares is the counter-move. The Up+B is similar, but Ike's goes back down, similarly to Kirby's. And the A moves are just entirely different. I think we'll be seeing a Fire Emblem character that is more similar to Marth/Roy. Or at least I hope so.