Erhm, well it's difficult to explain the technical details but Intel and AMD before that have gone the way to lower the frequency but to make more computations per clock cycle. This is mainly because they want to speed up existing software for a general platform x486.
IBM on the other had has gone through with the frequency increase, they keep the chip as 'simple' as possible and optimize for speed. So i do think the cell will be available in a 5 or 6Ghz version. (most likely there will be multiple versions with different speeds)
But this is just dedicated hardware, it is meant for the industry and if you try to use it in consumer enviroments you'll end up with industry standard costs and then you'll have 20-30million budgets for movie looking dragons flying around crashing together with your sixaxis on the floor.
Oh and besides, Sony won't bring out those high frequency versions with the PS3 just like they won't bring out a Blue-Ray drive actually faster then a DVD drive. (tough they did it with the PSP-lite) Just remember that they had to cut down on the amount of cells because of yields.
All the technical advantages will be converted to a PS3 witch costs less to produce, not to a better product.










