Currently, the only Fire Emblem games available on the Nintendo Switch are Fire Emblem Warriors, and Fire Emblem: Three Houses. For a franchise that includes over 15 games, spanning from 1990 to the present, that isn't much of a selection.
3DS titles such as Echoes, Awakening, and even the annoyingly disconnected Fates would feel right at home on the Switch thanks to their portable origins. It might be asking for too much, but a few Fire Emblem titles from the GBA could also be ported, just like they were on the Wii U. The GameCube installments seem too far out of the realm of possibility, though.
Regardless, the return Fire Emblem's tactical RPG action and loveable casts could create tons of new fans while still managing to please the current ones who just want to comfortably replay old favorites.