This will probably never ever happen, because:
1) They were not in the Heroes poll
2) The game was not super well-received by core fans
3) The feel is completely different than the setting of Heroes
Despite that, I still wouldn't mind seeing them toss in characters from #FE into the game. Am I alone on this?
Also, if they did do this, the #FE characters would be the only people to know that your Summoner weapon is a gun...