So we can’t just abandon them and say ‘Hey, it’s time to move on to the next thing.’ Of course we are working on NX and looking at the experiences we can bring to that platform. But first our job at this point is to support the consumers who have purchase Wii U and make sure that they have software experiences available to them.”
Source: http://mynintendonews.com/2015/12/03/nintendo-intends-to-continue-making-software-for-wii-u/