I'm with Julian.
I think most of the things we want more power for are 'embarassingly parallel'. So never mind dual processors, I want lots.
This is a definite hurdle to jump, in the same way switching cache architectures for the StrongARM was. But I think it will be necessary at some point, and since ARMs arn't being made as fast as other architectures, it would be nice to be sooner rather than later.
(I say this without any knowledge of the probably considerable engineering involved.)