Now, it will be up to third-pary publishers whether or not they want to release their game on the PlayStation Network or not, but what kind of dumb publisher would throw away PSP Go! compatibility right out of the gate?
And just to address a comment I saw over there, what happens to your UMDs when the PSP Go! comes out? I'm pretty sure your UMDs and PSP-3000 will work just fine even after the PSP Go! comes out; they won't automatically vaporize.