On the official Mana Twitter site, footage of what looks like Seiken Densetsu 3 on the Nintendo Switch has surfaced. No other details were revealed, but there you go. 

A Square Enix mobile developer has recently talked to Famitsu (via Siliconera) about a pair of new SaGa and Mana games which will "stay true to all [our] memories from the [SNES] and PlayStation era." The developer also mentioned that Square Enix's second mobile division would be "helping out" with the games.