I'm guessing we'll get a small bit dedicated to some more in-depth mechanics and how the route system is going to work. We'll also probably get a look at Eugenics Simulator 4 if that's still in the game.
I'm mostly expecting some info on how the game works past the earliest bits and the formation/skill stuff. Oh, and we'll for sure get gambits.
If we are getting an FE rep in smash, I want it to be someone like Camilla, an axe-wielding, flying magic user.