A good question since Sony is effectively winding down development on the console. Sure, the Vita has its champions at Sony, but how many months will it be before they're reduced to polite requests for hand-me-down PS4 versions?
So, you're an indie, with a great mobile or PC Unity game and you want to get it running on the Vita, how hard is it? Apparently, not too hard according to Baka Neko with a port of Project Light in the works. The summary seems to be, porting code and getting it running is very easy, if rather slowly for effects heavy titles.
With optimisation, those effects should work on the Vita, and the frame rate can be improved to playable. Hopefully, there will soon be a public resource of common/easy Vita optimisations to encourage others to have a go at bringing in Unity titles.
There's certainly lots going on in the Unity ecosystem, and most of these games look like a good fit on the Vita. Will developers start spreading the word? Or is the official release of Unity too little/too late for the handheld?