IBM shall debut POWER7 for the server market in the summer of 2010. The PlayStation 4 shall use a cost effective version of the architecture custom designed for Sony's specific needs.
FGNOnline currently has info available regarding specifications and performance is that the PS4 implementation of the chip shall use 6-8 cores, 24-32MB shared L3 Cache, Quad threading per core, and a double precision performance approaching 200GFLOPS.
The CELL chip which powers the PS3 is capable of 15 double precision GFLOPS. The CELL chip which powers the PS3 is capable of 15 GFLOPS double precision. This would give the PS4 a performance leap of over 10 fold over it's predecessor.
If true the PS4 would indeed be a graphical powerhouse when debuted sometime after 2010. I'll have to chalk this up as an rumor for now until I hear otherwise.