Not Metroid specific per say but here are titles for anyone looking to get their Metroidvania fix on Switch in the mean time:

Hollow Knight
Ori and the Blind Forest
Bloodstained:ROTN (Switch version soon to be patched to sort out the issues)
Bloodstained:COTM
Castlevania Collection
Steam World Dig 1+2
Dead Cells

Upcoming in Jan 2020 Hollow Knight Silk Song will be one to look out for.

What a great list, man.

But, I wouldn't include the Castlevania Collection because it's mostly the old NES and Gameboy games and those are rather just traditional Jump 'n' Runs when you break them down. Great games for sure, but no Metroidvanias. Those started with SotN, but of course you knew that.

In the poll I picked Metroid 5 because I want the series to continue. A couple of years ago I wrote on this site how I imagine the next game to be. I would love if it was staged in the capital city of the Galactic Federation like we saw it in Other M. One big metropolis with several different borroughs where Samus might grapple around on street lights and morph ball through ventilation pipes and the sewers, battling the Space Pirates on broken highways in between burning cars. The final showdown might happen in the head quarters of the GF on the roof in heavy rainfall and lightnings in the background.

But please, no more Ridley, he has died enough deaths now in this series. It's not funny anymore to have him cloned time and time again, no matter how much of a fan favorite he might be. Make a new villain altogether.

Ooo, I like the idea of Samus in the GF capital. I've been thinking for a while that a city would be an interesting setting for her, because the peculiar thing about cities is how isolated you can feel even as you're surrounded by people and man-made environs. I just wasn't sure how it could work, as her running around in full armor doing acrobatics in a city would be immersion breaking. This isn't Mario after all. But perhaps if the city were laid siege to by the Space Pirates, that could work. You might come across the occasional survivor, but otherwise just be playing Metroid in an urban ruins setting. Perhaps there could be a section of the city sealed off where the attack hasn't reached that tries to continue life as normal while the war rages outside, and Samus could go Zero-Suit in those sections, though I'm not sure what she'd do. I would enjoy the world-building potential of a populated city, though.

I agree on Ridley, the poor bastard needs to just be laid to rest. We need another villain that can be recurring for a while. Maybe he could make an appearance in some sort of Star Trek holodeck style training room just as a throwback for fans, but he needs to be retired from the plot.

I picked "Other"

I'd love to see a Metroid open-world RPG taking place across multiple planets, with a lot of cyberpunk style elements. It can maintain all of the deep dives into the underground, but I want something more to the Metroid experience.

My second choice would be a Hollow Knight inspired Metroid game.

Thanks, I'm glad you like the idea. The city indeed needs to be mostly empty to maintain the typical Metroid feeling. Also many places could to destroyed so Samus could squeeze through the debris. Also that would add to the tension. But yeah, a contrasting area where everything is still okay is also a good idea. I like that. 

The final game will probably be something completely different lol, but whatever.

Has it been confirmed that Silksong is a Jan 2020 game?

It's currently a targeted date so will likely change.

At least one person has taken the bait on Ring Fit Samus' Adventure. Show yourself! Let's hear your ideas. I have a few myself, but I'm interested to hear someone else's. And please tell me how loud the groan that would emanate from the internet if such a thing were to be announced.

If Metroid Ring Fit were announced as the replacement for Prime 4, I'm pretty sure fans would burn down all of Nintendo's studios, then light fire to themselves.

If Nintendo were to do something like Ring Fit for Metroid though, I'd rather they combined it with Labo VR, made a strap to hold it to your head, then had one JoyCon on your leg to make Samus run and jump, one on your arm to operate her arm cannon, and you'd turn by turning your head wearing the strapped on headset. Just call it Metroid Fit VR Experience or something, and make it play like a watered down Prime game. But all of this just to get people interested in the idea of VR Metroid.

Then for Gen 9, have a fully integrated VR mode for the next console and have the Switch 2 port of Metroid 4 basically have the entire game playable in VR at a quality equivalent to Playstation VR. I think the Metroid Fit game would sell decently on the Switch to a starved Metroid audience that likes the idea of Metroid VR, and then Prime 4 could be a launch title for the Switch 2 that would do to Metroid what BotW did to Zelda.