To put it in perspective, we went from 6Gflops GPU in Xbox 1 to 240GFlops GPU in Xbox 360. That's a 40x increase in raw power along with massive shader improvements. The best raw power increase we're getting this gen is about 8x, so no... nowhere near previous generational leaps, that's not really up for debate.
EDIT: To match the raw power leap from 6th gen to 7th, PS4 and Nextbox would have to be pushing 10TFlop GPUs.







