Saturo Iwata said that the way Gamecube is designed, you could say it doesn't have main ram, just L1, L2, and a huge 24MB L3 cache.
So Nintendo will not mix in GDDR3 memory or any other memory, it will be more 1t-sram if they put more in.
And IF the "GPU has 32 pipelines, shaders and blabla (meaning it would whoop the PS3 and 360 GPUs no problem)", Nintendo won't sell Revolution for $150