The Persona series is too big for for a handheld and despite Sony's attempts to stablish a good lineup for the Vita (which has been achieved), they still haven't found a killer app, something that turns their portable device into a need for the gaming community.
But we already know the solution, don't we?
If you make a survey and look for the actual reason why people buy 3Ds and Nintendo handhelds in general, the same franchise will come on top 9 out of 10 times: Pokemon.
So lets make a case here. Given the scenario in which,
1) Sony acquires full rights of the Digimon Gaming franchise.
2) They allocate a dedicated studio that can focus on periodical releases.
3) And finally turn the sporadic status of the franchise into a strong portable IP.
Will you buy a Vita?