From what they have said about a possible Switch follow up it seems like they're still working on the concept and specs.
This is true but I think they're being cagey as Nintendo is wont to do. They've always gone into prepro on a new system shortly after the current one launches, so they have 5 years of R&D under their belt (during the splurgiest R&D period in Nintendo's history). I think the system is far enough along in terms of design (
possibly explaining
some of the leaks) but Nintendo is probably apoplectic over the current state of getting chips, so they're not going to charge in guns blazing when they know they're low on bullets.
Conspiracy theories say Nintendo intentionally limited the initial stock for Wii but I don't think that was ever true. I think they were legitimately caught off-guard by the insane popularity coming off the GameCube, and I think that memory still lingers in the current executives' minds.
Right now they're probably selecting which specific CPU/GPU to use, and I'd expect that to be all that's left to do at this point aside from stuff that comes later like services and software. And seeing how they publicly dumped Nvidia mid-development for the 3DS's GPU, it seems like Nintendo knows how to swap similar chips while still achieving their desired end-product.
