I think Nintendo is way too hesitant to bring back motion games. I don't think this was a fad, a properly made and properly advertised Sports Resort may sell 20 million copies and should not be too expensive to produce. Namco (Go Vacation), Ubisoft (Sports Party, Just Dance) and Konami (Hyper Sports R) are actually trying it, but to kickstart it I think Nintendo as the platform holder should do something and advertise it properly.
I also have another idea in the back of my mind. How about a cardgame or boardgame utilizing NFC-capabilities? So, you put the Joycon with the NFC-scanner on the desk and interact with the game shown on the TV by putting down cards or boardgamepieces, matching the situation. I think it should be possible to do something with that.