Sony gets tons of third party support in Japan. There has been no real need for first party support from Sony in terms of the Japanese market. The support for the PSP is still incredible, and because the 360 was basically non-existent there, multi-plats were essentially exclusives. They also had a ton of real PS3 exclusives, as well.
The only problem right now is that third party developers have been content to stay with the PSP. A LOT of new PSP games have been released recently or will be soon. We just have to wait and see if these smaller studios move on to Vita development after their last PSP titles have been released. Judging from comments from Sony executives, I get the impression that they're going to be working hard on convincing developers to make the jump.
I've said it before, but I think we'll see a surge in Japanese developed Vita games about a year from now. The transition from the PSP is going to take awhile.
