The-MMMs wroteto my knowledge (i may be wrong) all Ps3 games run around 720p - yet PSN games (some of them) do run at 1080p
There IS a list somewhere, but im pretty sure (and yes i know for some games the TV reports 1080p but it isnt) same applies to the xbox btw.
Anyway, yeah i suppose the next gen will have proper native 1080p resolution, with better AA, and at least some more RAM - i can only imagine how the XMB and Dashboard will evolve.
PS3 was made to run 1080 p games, few games run at 1080p ( Metal Gear Solid 4) while the rest run at 720. Lately however, more games are made supporting 1080p , which means they are beginning to use the full power of the PS3. So i guess it will stay for some time before the PS4 since they just started using the full power of the PS3.