John Lim is an artist over at Nintendo, and his resume and LinkedIn profile both make mention of an unannounced project. The thing is, we don't know if these mentions are tied to the same project, or two projects.
First up, his personal resume shows a project from NST which isn't set for release until 2023, which is a pretty long development time! A game that is 5 years off isn't unheard of, but it definitely is a pretty lengthy dev period.
Second, John's LinkedIn makes mention of an unannounced project that he worked on for 10 months. Again, we don't know if this is the same project as above, but one would assume it is.
Man, if the date is right on John's resume, we're going to have to hang tight for quite some time to learn anything about this! I have NO idea what it could be, but I'm sure smarter people out there could put something together.