I doubt that Marth would be out just because Ike is in. Marth started the whole entire FE series. Adding other characters from FE without Marth would be like adding characters from Mario without Mario.
Not really.... Marth isn't necessary to the series FE series like Mario is to his.... Mario is in every non-spin off game of his series. The games pretty much revolve around Mario's adventures, and any game where Mario isn't the main character is a game about Mario's nemesis Wario or Mario's brother Luigi (and that was only one, spin-offy game). Mario didn't just start the Mario series; he is the Mario series. Marth is hardly to Fire Emblem what Mario is to his own series.
That being said, Marth is definitely an important character to FE and he could very well be included. But I suspect that Ike and any other more recent Fire Emblem characters will completely replace Marth and Roy.






