So in June 2015 Miyamoto stated in an interview that they had footage ready for Zelda U that could be shown at E3 but Nintendo decided to not show it because they wanted to make shure that what was shown could meet the actual possibilities of the Wii U, now that we know that Zelda U is coming also to NX I think it's pretty obvious what was going on at the time: Nintendo focused development solely on the NX version, so they couldn't show the Wii U version because it was "early" in development and they weren't shure what kind of graphics they could get on a less powerful hardware, this is also supported by the fact that the Wii U version isn't coming out this holliday season: that's because it isn't ready, while the NX version most likely is almost done!
