Persona is Sony exclusive just like SMT is Nintendo exclusive. Remaking a game for a platform that doesn't have the original is a bad idea especially for a JRPG, not to mention its dark themes have less of an audience on Nintendo platforms.
How does this make sense when there are SMT games on the DS/3DS?
The only way I see a P5 port coming to the next Nintendo handheld is if they take a long time before they port the game, and by then the Vita is abandoned and Sony don't have any plans for another handheld. Even then they might just do a PS4 port instead. So either way I don't think it's likely.