Today during its Fire Emblem Direct event, Nintendo announced that Fire Emblem Warriors will be coming to New Nintendo 3DS and 3DS XL when it launches in Fall 2017. The game was originally announced at the Nintendo Switch Presentation for Switch alone.
The game will be handled by Koei Tecmo's Omega Force and the same team that was behind Hyrule Warriors, so Team Ninja will probably be pitching in. The same gameplay trailer shown at the previous event was delivered here.
So far, Fire Emblem Awakening's Chrom is the only character that's been featured in gameplay. This is leading fans to speculate who will be in the final game. It's likely that Nintendo will want Omega Force to focus on the more popular Fire Emblem Awakening and Fire Emblem Fates casts, but I can't see them leaving out some classic Fire Emblem characters.