It has been revealed that Marth will return in the next installment of Super Smash Bros.
Marth debuted in Super Smash Bros. Melee alongside Roy, and appeared again in Super Smash Bros. Brawl. Marth was the main character of the first Fire Emblem game, which is probably the reason he is returning.
Many people, myself included, are hoping to see a character from Fire Emblem: Awakening join the cast. If that does happen, it seems likely that Ike won’t be making a return. However, I can’t say that for sure, and if they decide to have more Fire Emblem characters in the mix, I’m not going to complain.