I think it will be the best selling Metroid game at 5 million lifetime and satisfy those who are fans of the series.

That is all.

Just for clarification…is that enough? To me, as a Metroid fan, it absolutely would be. 

From a business perspective? It should be, considering how that's how much the original Prime Trilogy sold. Admittedly development costs have risen, but even in the HD era of Nintendo, 5 million was around what games like Super Smash Bros 4 Wii U, Splatoon, and Mario Tennis Aces sold.

People online whine about yellow paint. I am not a fan myself but so many people are lost without it and are not terminally online like us. Not enthusiasts like us. This nerd character has yellow armor. He is literally yellow paint the character. He will be in the game for the length of a fart in the wind. Sure longtime Metroid fans like me don't need him. However this is the beginning of a new trilogy(?) Maybe. They want more than the typical 1.2 or whatever million sales of Prime. This game is aimed to cast a wider net. I'm okay with that. It seems the choice is either back to long droughts with no new Metroid game or some yellow paint with more frequent releases.  Fire Emblem did the same thing with Awakening. They made it more accessible. After that the series went from barely getting releases in the west and knocking at deaths door to being a staple series. Metroid is not in dire shape like FE was before Awakening but Prime needs to grow.  

MP4 into goes hard

I am not a fan of the yellow paint and hold out little hope that Samus (i.e. the player) can mute their comms perhaps have a dot light up in the HUD in place of their dialog. I hated Navi in Skyward Sword with a passion. I cannot imagine I will enjoy this part of the game. All that said, to @Leynos point, if it makes it more accessible to a new audience then so be it. I am too much of a fan of the series to let something potentially annoying deter me from a purchase.

To @HyrulianScrolls point I think you nailed it, but would a divisive game be the worst thing for sales? Controversy should result in extra discussion (see arguing) and might help a niche title. That is of course if its fan reception is better than that of Other M. It kind of pains me to admit it is niche since I think so highly of the IP. I will disagree in my range and say 88 to 90 on the meta.

MP4B has a NS1 file size of nearly double that of Tears of the Kingdom. Yeah… I’m feeling confident saying that had this game released a month or two prior, it could’ve been a frontrunner for GotY. But maybe I shouldn’t get my hopes up too soon. Only a few more weeks until we can know for certain!

It beats the Xenoblade series.  

Wow…I didn’t realize how on par these two series are. Both are quality gems in their respective genres with a die hard fanbase and an intimidating gameplay style that scares away casuals. Nintendo does seem to value both and that is in line with a lot of chatter about Nintendo liking to have good representations in each genre, even if they don’t sell that well. It makes for a wide variety of options on their consoles. 

Usually when Nintendo takes a long time to make a game, it turns out to be really special. And Nintendo really took their time with this one.