Obviously development started on the ps3, though idk if I'd consider that smart. Atlus has a history of lagging behind on their software being on recent hardware. I think it'd be better for Atlus and especially Sony if they made it exclusive to PS4 because that game has enough fans where a lot of them would buy PS4's, especially ones bundled with P5. And it has the benefit of being a better game tech wise since it wouldn't be restricted by the PS3's hardware.
It'd be better now if Atlus moved straight to the PS4 and developed new games, especially SMT, for that because people are craving games, especially RPGs, on their PS4.