Reuse the Cell, but instead of using a single core hyperthreaded controller main CPU, use a Quad core, 8 thread CPU controller mounted with 24 SPU's . That's exactly triple the SPU's on the PS3 Cell. R&D costs would be low, and performance would be high. Dedicate 3 to the OS (for some AWESOME in-game OS) and 3 disabled for yeild. That leaves 18 for games (again, triple the PS3). Then use a mid-high end Nvidia card (Sony probably won't switch to AMD cards) which would also have low R&D costs.
And an extra benefit, if they clock the Cell at 3.2GHz (like the PS3) then it will have hardware BC with PS3 games (as long as the GPU could virtualize the RSX)







