Even if all that bandwidth was available it would be near useless with the GPU the wii U has, it's like a 6 lane highway leading into a small village, there will never be that much traffic on it...
I would have been curious to see if the PS4 would have shipped with a 1gbps edram (not dure if it was not dram... whatever, some really really fast buffer) module + some DDR3 as Cerny said they contemplated doing... that's mighty fast!