I don't think sales are the Metroid series' problem. As long as the games sell in the millions Nintendo seems content to make them. 

It seems to me that the lack of development of new Metroid games had more to do with internal workplace shifts which hindered the ability of Nintendo to produce good Metroid games. 

Retro Studios wanted something new after Prime 3, and a lot of the old staff had left anyway. Every new developer Nintendo worked with ended up shaping the series into something fans didn't like. The previous attempts at developing Metroid Dread reached technical or creative limitations. 

That Nintendo decided to develop Dread after Samus Returns' sales signifies to me that they are happy with the games in so much as they break even profit-wise. Whether the game is well recieved seems to be more important to them.

This makes sense too. Nintendo understands that their core base needs to be excited for other people to be excited about their systems and games in the long-term. Metroid might not be a huge seller in itself, but it has a strong fanbase that almost 1:1 overlaps with Nintendo's and this helps ancillary sales of other games in that it brings word of mouth/media coverage to the system in general. 

I still think Dread will probably sell over 2 million, but if it sold only something like 1 million I don't see Nintendo having a huge problem with that. 

The game's development costs probably are mid-tier/"AA" level. 

There will be another Federation-created Ridley clone, you can bet on it.

I wish they would give Kraid a chance instead to be honest. Maybe bring to reality the scrapped Metroid Prime boss battle? Meta Kraid would be awesome to have...

Day 1

It also didn’t help that Sakamoto’s team (formerly R&D1) was absorbed into the Software, Planning, and Development (or SPD) team under Iwata. They mostly focused on supervising projects from their partners. So, Sakamoto had to look elsewhere to get help in developing new Metroid games.

https://m.youtube.com/watch?v=ykfRsShBHsM

The funny thing is I 100% agree with this when it comes to Metroid, I'm not trying to sound crazy when I talk about sales mattering. There's something about the series that I think it's reasonable to say makes it more important than say F-Zero or Golden Sun to Nintendo, and I think it's that it probably has a higher unit-pushing ratio then say F-Zero (that is to say, probably more people would skip out on Switches if no Metroid than is the case with F-Zero, even if both series are relatively niche) and also that Metroid is just one of their most acclaimed series ever. It's sort of like how for a long time Sony felt it necessary to platform Team Ico games. 

However, and maybe this is a poor assumption on my part, I do sort of think that might change with theses games. If these games didn't sell as well as some of the peaks of prior Metroid games (for example, Prime 4 not selling as well as Prime/Metroid 1, or Dread not selling as well as Fusion/Metroid II (I don't think it selling worse than 1 would be their breaking point), that would indicate a surprisingly low amount of interest for a series that for the first time in forever is having all the stars align. 

Honestly, the likelihood of that even happening (sales being that low) is pretty small to begin with. And honestly, I wouldn't be surprised if they just continued treating Metroid much like how Sony used to treat Team ICO, and in that sense I'm not putting all my eggs in  this one basket. I just wouldn't be surprised if it changes for these games and, given super mediocre performance, it goes on hiatus again. Not out of some dismissal of the franchise, just out of it not being a big priority. 

TLDR: I agree with you and have always thought about Metroid that way, I just think it's possible that might change for these games. And moreso, my point is that if they got super mediocre sales, I wouldn't blame Nintendo for putting the series on another long hold. Not that I personally think that will happen. 

With a bit of thinking, i honestly don't think it'll do bad sales. Overall, it's getting a good reception and the pre-orders are doing fine (both the special edition and the normal one are out of stock on Amazon). Initial sales with the push that might bring the holidays window, are going to be OK. After that, It will depend on critics and mouth to ear to make it prevail through the time and give it legs. But THIS seems to be unlikely to happen unfortunately.

I hope for 3Millions and i'll call it a Win.

It's nice to see that they haven't artistically homogenized Metroid as they kind of tried to do with Federation Force's horrendous cartoony chibi look; with nearly all of Nintendo's first party catalogue sporting cartoon art styles, it's refreshing to have something semi-realistic in their lineup.

Don't think a game called Metroid Dread could have looked like a typical Nintendo game, anyway, Also, I still wonder why they decided to make Federation Force look like it did.

Infections! Vaccines! Face coverings! Social distancing! Fuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuunnnn!!

Seriously though, this game really does look like it'll be a lot of fun. The announcement took me by surprise too! The graphics don't. It's mainly the bland color scheme (too much white) and the one-sidedly mechanical vibe of it all that I dislike. Not against a limited color palette, but many of the combinations I'm seeing as yet look pretty generic and boring and the whole thing feels more cartoony than I can take all that seriously, or at least as seriously as I'm supposed to. But what I do like is a lot of the water effects, the lightning-fast pacing, the E.M.M.I. horror element, the seamless transitioning between 2D and 3D scenes, and what sure seems like the sheer breadth of the world available to explore and discover here. And also the promise of a definitive conclusion to the Metroid saga! And also also, Samus's new suit. I know I just complained about the art style overall here, but I'm giving the suit a pass on that 'cause it just looks cool!

What I'm expecting here is for Super Metroid and the Prime games to remain my favorites in the franchise, but Dread looks like it has the potential to become my second-favorite 2D Metroid title. That it's being made by the people who gave us Samus Returns is alrighty by me. I found Samus Returns imperfect (a bit more action-focused than I'd really prefer for this franchise), but the best Metroid title in a decade when it was released back in 2017. This looks way smoother and more refined than Samus Returns, I might add. The $60 asking price took me aback when I first saw it because I'm still not used to seeing that high a price requested for a 2D game, but then I looked at the storage space it requires and felt like there sure seems to be a lot of content here, so...maybe there's half a reason after all. At any rate, I'll gladly pay it! I mean I doubt this will be among the best-selling games on the Switch, but I also don't care. Metroid has never been Nintendo's most popular franchise and I'm okay with that. I DON'T want another Federation Force type experiment aimed at expanding the franchise's appeal at the cost of its soul. And honestly, I'm so starved for more space bounties to hunt that I'll pay about any price for the chance, especially if it promises all that this game does.

Bottom Line: I'm hyped too!