This prediction would make sense if the argument was that Retro messes up in the same way as the original developers of Metroid Prime 4 and therefore the game gets canned altogether.
But as it is, it's a terrible prediction. It expects a very long development time in conjunction with a short lifecycle for Switch, plus Nintendo's willingness to use a low-selling IP that went through troubled development as showcase title for their next console.
They are still looking for the key art director. They are clearly only in early pre-development phase, and actual development will take 2 full years at the very shortest. There's no way this is releasing before another 3 years, that would be a "normal" development time for a Nintendo project, not a long one. And 3 more years would also be a normal 5 year system cycle for Switch. Add another year because of the Switch's success and we would still almost surely see the successor in 2023. Nintendo will be well aware of this, hence why I think they would have the foresight to want the project moved to the successor.