Yes I think DLC would work really well and benefit Nintendo greatly because everyone would buy them.
Mario Kart would probably benefit the best from DLC because people get really attached to certain tracks and a lot of times thoose tracks dont make it to the game therefore DLC could work well for Mario Kart. Also making tracks shouldn't be that much work so it won't cost t o much for them to make sense there basically porting the tracks.
Making DLC for Smash Bros will be much more difficult because creating and balancing characters is not a simple task. Also by making some characters only available through DLC didvideds a community. If Nintendo really committed to it I think it could work but it would take a lot of time and probably cost more money then its worth.
Survivor Millennial vs Gen X!!