Man, people are still hung up about Nintendo/Sony not swooping in? Both of those options are bad decisions for us (most of us) for different reasons.
Yeah, Nintendo would definitely have a lot to reap from mainline SMT at this point (especially since 4 not only did a lot better than other mainline/non-Persona spin-off titles in the entire series, but at least its JPN sales are comparable to PS2-era Persona 4). And they would definitely benefit from their smaller franchises like Etrian Odyssey (or maybe even Radiant Historia). But there is a big risk in Persona not having as much of a crossover on Nintendo platforms (thus, you run the risk of sinking one of Atlus's big moneymakers).
On the Sony side of the fence, sure, you would still have Persona. And maybe you would get that super awesome AAA budget HD Persona 5 on PS4 or something. But that would very much sink the mainline Megami Tensei games (especially in light of 4's sales), Etrian Odyssey would be dead, Trauma Center would be even deader than it is now, and there are still potential localization hurdles based on "old school graphics" like the ones that plagued PS1 Soul Hackers and allegedly PSP Devil Summoner. So for the price of keeping Persona, you potentially prematurely cut off a renewed interest in the old school style of mainline MegaTen games by suddenly switching platforms (and this worked out so well for Namco-Bandai when they were playing hopskotch across platforms before they settled on the PS3).
Yeah, Nintendo would definitely have a lot to reap from mainline SMT at this point (especially since 4 not only did a lot better than other mainline/non-Persona spin-off titles in the entire series, but at least its JPN sales are comparable to PS2-era Persona 4). And they would definitely benefit from their smaller franchises like Etrian Odyssey (or maybe even Radiant Historia). But there is a big risk in Persona not having as much of a crossover on Nintendo platforms (thus, you run the risk of sinking one of Atlus's big moneymakers).
On the Sony side of the fence, sure, you would still have Persona. And maybe you would get that super awesome AAA budget HD Persona 5 on PS4 or something. But that would very much sink the mainline Megami Tensei games (especially in light of 4's sales), Etrian Odyssey would be dead, Trauma Center would be even deader than it is now, and there are still potential localization hurdles based on "old school graphics" like the ones that plagued PS1 Soul Hackers and allegedly PSP Devil Summoner. So for the price of keeping Persona, you potentially prematurely cut off a renewed interest in the old school style of mainline MegaTen games by suddenly switching platforms (and this worked out so well for Namco-Bandai when they were playing hopskotch across platforms before they settled on the PS3).