Ofcourse people shouldn't be concerned about the Wii U's ability to do HD gaming.The PS3 subHD games were even lower res than the 360's subHD games, probably due to that.
Either way, we're going from the Wii (which had essentially a whole 3MB of VRAM to play with) to a console with 32MB, and the 360 was limited to 10MB and DVDs. I'm not really concerned about the Wii U's ability to do HD gaming.
But they also shouldn't overestimate release priorities, porting timeframes and human resources.
It wouldn't surprise me at all if the Wii U version of CoD still happens to be native subHD.