I got just one objection about future versions of the Cell for future Playstations: SPEs used in the original Cell were very basic, development continued, and in 2008 IBM released a version for supercomputers that kept for years the record of FP performances per watt. http://en.wikipedia.org/wiki/Cell_%28microprocessor%29#PowerXCell_8i
By now, and using just 8 or 16 SPEs in a single CPU, those evolved SPEs should be quite cheap, and given the ratio by which they outperform PS3's Cell, they should be enough for next gen needs and, just increasing their number as their cost for each further drops, possibly clock speed and maybe with a few other refinements, also for the generation after the next, even if IBM lost interest in its further development.
Relying more on PPEs in the future, anyway, makes sense.







