I'm reluctant to put any stock in these estimates. What does "50% more powerful than PS3" even look like? Also, developers probably don't have final dev kits. Nintendo's final hardware could end up being significantly more powerful. Or not. Until someone releases the set specs sheet, it's too tough to call. We've been hearing wildly different claims, even from the same developer during the same interview.
In any case, I think Nintendo will be fine on the hardware front. WiiU is already more powerful than the current hardware and anything MS/Sony come out with won't make WiiU look bad by comparison because graphics are beginning to plateau and budgets haven't gone down.