I'm kinda surprised that there hasn't been an announcement, teaser, or hell even a leak of the next fire emblem game by now considering the commerical success and critical acclaim of 3H, even though it's only been like two years. Hopefully Nintendo is giving them longer dev cycle with a higher budget now that FE is now solidly a AA-franchise with mainstream awareness and not just "that jrpg that steals smash bros slots."
I really liked 3H even though I bounced off of Fates pretty quickly but it definitely has some areas that could use improvement. There's the much-maligned monastery and first act that make replays to see the other routes a slog and quite poor graphics. I get that the Switch is basically just a $300 tablet but there are textures legitimately look like something from a PS2 title.
Optimistically speaking, the switch is 1/2 to 2/3 of the way through it's lifecycle, and it would be weird to wait to capitalize on it's success until the end of the generation, especially with Nintendo's increasing fondness of season passes and premium online features. At least there's a massive backcatalogue of old titles to play in the meantime, and maybe it's a good thing, considering what a frequent/damn near yearly release schedule did to Pokemon.