I'm impressed with the software the PSP continues to move. That's a good part of the Vita problem right there. Developers will switch over eventually, and might have already done so with games in production, but releasing a low budget PSP title looks to still be profitable. It just won't help move Vita units, though.
As far as what the Project Diva spokesman said, I wouldn't worry too much about it. Calling anything "extremely difficult" is a very typical thing for a Japanese businessperson to say. It at once lowers expectations, prompts support from fans, and puts them in a win-win position when/if they do attain the goal in question. It does not seem that he said there wouldn't be another sequel or even that there are no plans for it.
