According to an interview with Hayashida, they may do more or return to the Captain Toad level idea from Super Mario 3D World. He didn't make it clear about this being some separate eShop game or anything, but I'd really love that.
Hayashida wrote:We thought they were a lot of fun, so we’re really glad everyone likes them too. If enough fans express such enthusiasm, we’d consider doing something with this feature in the future. They weren’t inspired by smartphone games. The idea was to design a game that would become even more fun as you play through it, and this influenced the pace of the game, effectively increasing the rhythm. We felt that a short challenge with quick results would be a good motivation for players to advance onto the next course.