If you're suggesting they'd get more by making it multiplat, it's not going to matter much in Japan. Though maybe a Vita version of Zestiria could do a decent amount, but they seem content in just making one version of a game at a time.
With next gen consoles, the Tales fanbase will move to PS4 before anything because it's a Sony console.
I hope Zestiria is Bamco's last PS3 Tales. Game looks decent but if they want to expand on the idea of making a (kinda) open-world game, they'll have it easier with a more powerful console.
And, to be honest, I don't know if the Vita will be able to handle Zestiria. With proper work, it obviously would, Borderlands 2 is working there. But I noticed some harsh framerate drops in Xillia (in busy moments during boss fights, mainly. The slowdown was really noticeable) and that was a game without battle arenas. I'm afraid what could happen in an open-world game on a weaker hardware.
And, if they have to port anything. I'd rather choose them to port Vesperia.
And the Tales games are pretty much uprezzed PS2 games today, so I can't imagine Bandai-Namco would move Tales to PS4 anytime soon, or expect those fans to do so. Those games need to take a graphical leap before anything else, IMO.
It doesn't matter. I'm sure most fans don't care about it. I'd gladly take a "good looking" Tales of game obviously (or at least a cell-shaded one...) but I don't care if there isn't a big graphical leap.
I'd be satisfied with some extra AA, better textures and a improved lighting engine.
Right now I'm more worried about Zestiria story... I don't know what to think about what we've seen so far :/