It's quite likely that most reading these pages will, at some point in their lives, have signed a non-disclosure agreement (NDA). Even relatively simple employment contracts have them, though naturally major companies also trust third-party individuals and businesses with un-announced information. Naturally this leads to leaks, as Nintendo knows only too well.
Still, whichever leaks and rumours you believe in, related to NX, we can all be confident it's a thing that is happening. Joining the pile of reasons to believe units (or at least information about units) are out there, game maker and creative Stephen E. Dinehart IV has tweeted - hat tip to GoNintendo for the spot - that he's signed an NDA with Nintendo, hashtagging NX.
In recent weeks there's been some trolling from people making NX claims simply to tease (many of which we've ignored here) but we see little reason for that to be the case here. Dinehart IV has an interesting track record as a designer, consultant and game maker, working on some major projects. Over on his LinkedIn page he's also listed himself as an independent software developer related to Nintendo since January 2016.
If he is indeed making a game for the NX, perhaps its eShop, it could be a fascinating project. Through his Colorverse label his most recent game (for smart devices) was designed to raise awareness for World Elephant Day and the threat of poaching.
It'll be interesting to see what comes out of this in the coming months, in any case.