I think it is not fair to fear the Wii U will be ignored once the PS4/X720 out power it. The Wii was ignored for many multiplataforms because the X360 was already out and settled the base-hardware for the generation, but the Wii U will be the first to launch to the market and will settle the base-hardware.
The PS2 settled the base hardware for its generation and it had just 4MB of VRAM(enough for more than 10 years !). I think the Wii U will be OK for the third party support since will be the first to launch.