do you think they'll do both in one package, or would that be too big of a project?
Difficult to say. Never played them but read about the games on the various FE wikis, i think Thracia plays in between and partially parallel the storyline of Genealogy, so one package might be tricky to do.
And they're both full blown FE games.
I think doing seperate releases with expanded content like they did for Echoes: Valentia is the better way to do.
Depending on the scope of the potential remakes, they might be able to do a one pack for the first two GBA games and handle the jump from Lyn, Eliwood and Hector to Roy like the time-skip in Three Houses and Genealogy.
So they would have room for a standalone SS remake and don't have to "waste" three games to the GBA generation.