Personality-wise, Camilla is a very complex character--which honestly surprised me. That said, I'll be equally surprised if she's not in Fire Emblem Warriors--especially after Cordelia's reveal. Now we know for a fact there will be flying units.
As for Smash, I find her unlikely, since she's not the main character of Fates. To me, that would be like adding Soren in the game. Yes, he did play a major role, being Ike's advisor and all, but in the end he wasn't the titular character of POR. Still, there's no denying that Camilla's moveset would be unique. She wields both tomes and axes--the latter of which isn't used by any current representative. If she used her wyvern, then she could have multiple jumps.
At any rate, I think she at least deserves to be a trophy in Smash.