If I remember right, the port over to PS4 was actually pretty simple since they were already working on XV, and this team was more familiar with the PS4 hardware. In any case, the PS3 was way harder to develop stuff for than the PS4. I'd also bank that they are doing it on PS4/Xbox One in part because they were hoping for solid sales out the gate since the first print would have a demo for XV tied to them. I mean, their communication on that front was a bit iffy, but I'm sure that was part of the thought process.

I'd argue it makes more sense for Sony to want it on PS4 than Vita if they wanted it to boost sales of a console if there was some kind of deal (I'd highly doubt Sony would be funding this game since it is on Xbox One as well) just because they've all but abandoned the Vita. They still see a future for PS4, and it needs more games. The Vita would probably make more sense from a gameplay standpoint though. I'd imagine the game is designed more around be portable than on a console.

There's also no real reason to put it on PS3. Sure, it'd be nice for people who haven't gone to the current gen of consoles, but most people are focusing more on the current gen now. When you take into consideration of that fact that it's on Xbox One AND PS4, they really aren't limiting their sales that much if at all.