I'd say in some ways the Cell is more "multi-core" than other CPUs. Those SPEs run autonomously to each other. The only real interaction between them is explicit DMA between memory. Other than that, those CPUs can do pretty much any kind of computation other CPUs can, except they are pretty short on local memory.
In order to leverage all those Cell SPEs you have to design your software architecture and code REALLY well (e.g. tasks/jobs instead of the traditionally used threads). A byproduct of this is that the task/job code you design for this is usually easier to scale up to hundreds of cores as compared to a threaded model.
AMD Opteron Socket G34 can already scale to 8 sockets with 12 cores per chip package i.e. 96 X86 OOO cores.
Once you have code that will run on Cell, it is relatively easy to port it to the kind of multi-core you find on 360 and PC. The other way around is not true though if you didn't take PS3 into account. So in some ways while I hate Cell, it is also probably a good heads up on how software needs to be designed moving forward. So I think tech will be more ready for hundreds of core than we might think, if that ever happens. Maybe with the Epic thing, they aren't sure if the hardware will be powerful enough.
Anyway, not that this has much to do with Natami. Thinking of SMP on there seems very ridiculous at this point when its not even being done on AROS/Morphos/AOS4.x. I think if anything it would make more sense to extend the CPU with SIMD first.
AMD redefines it's on-chip GPU as "SIMD Array" i.e. the "GPU" is marketing terminology from NVIDIA. ATI GPUs ussually includes it's own command processor.
http://arstechnica.com/business/news/2010/05/ibm-cheats-on-cell-with-nvidia-tesla-for-servers.ars"IBM cheats on Cell with NVIDIA Tesla for servers"