Website thesixthaxis.com has a video showing the Sony Xperia- essentially a PSPhone -in action. In the vid, the as of yet officially unannounced handset is shown running BioHazard 2 and Rage Racer.
So while it looks as though it definitely will play PSOne ROM's (purchased through the PSN?), whether it will have it's own unique gaming library has yet to be seen. Since the phone runs the Android operating system, it's also possible that it'll simply use the 'droid App Marketplace for games in addition to some kind of Sony storefront.
In any event, as stated above, it hasn't even been officially shown yet- so there's more than likely some things to be worked out on the functionality end before that happens (maybe at e3?)