It sounds like they're basically restarting Metroid Prime 4 from scratch with Retro this time, so... boy, that's going to take a while. I guess we don't have to worry about getting hyped to see it at every Nintendo Direct, because we definitely aren't going to see it any time soon. To be honest I wonder if it might end up missing the entire Switch generation; if it takes 3-4 years to make it's definitely possible. Samus might be staring down the barrel of a two-generation-long absence from Nintendo home consoles.
And I have to wonder what happens to the game Retro Studios has been making until now. The rumours said it was that Star Fox/F-Zero racer, but even those rumours were over a year ago and we never saw anything to even hint at them being real at any of Nintendo's shows. Hopefully whatever they have been working on hasn't been cancelled in favour of Prime 4. They haven't released a new game since Dankey Kang Trapical Freeze in 2013.
This is from the senior editor at Game Informer:
I actually sold my Switch late last year, because it was already caked in dust and there was nothing I really wanted to play on it until Bayonetta 3, Metroid Prime 4 and hopefully a Persona 5 port. I'll hop back onto the Switch train once the new, upgraded model comes out (whenever that ends up being).