I think just about any console saw great improvements compared to launch games. If it's what we call "secret sauce", XBox One will probably have it, be it DX12 or not.
But having more improvements that comes faster and has more impact than on PS4 to the point it closes to a significant level the current gap with PS4 is a totally different talk. The gap is currently wide and PS4 with massive amount of fast memory, a better gpu and more first party teams seems to have a lot of room for improvement.







