As far as I know, there aren't any plans for full T1 or framebuffer support. Even if it was done it would cause such a speed-loss it wouldn't be worth it save the fastest of games.

I'd like to post a link to an older thread I created related to this one :
viewtopic.php?f=12&t=3176

While PSP can render two textures fine in two passes it not so easy for N64 texture using T0+T1 since they seem to use alpha on only one texture to screen both textures which is something you cant do in a "cheap way" when rendering in two passes. You really need both textures to have same alpha to do it on PSP and while one can create a new texture copying alpha from one texture to the other and mess about it not really practical when we need all the speed we can get.
So back to square one...
But then again, we aint missing out all that much not having T1 on PSP