Ike has some popularity going for him now with the last two Fire Emblem games and also being in Smash Brothers. I wouldnt be surprised in the least if Nintendo made another game featuring him because hes pretty much the current Fire Emblem mascot. I think having him in the game would sell a significant amount of copies compared to without him.
Your idea of having Greil's story featured in a new game is a great idea. They could keep many memorable characters such as: Greil, Tibarn, Digensea, Zelgius, Sephiran, Ashnard, Laguz nobles, Stephan, etc., etc. etc. Lots of possibility there. Hell they could even slap Ike on the cover as a kid to sell a few thousand more copies even if the game didnt feature him as a playable character.







