At this point, not putting it on Switch 2 would be a big problem. This is a prestige, hardcore-oriented game for Nintendo. It's also an expensive one, between its initial failure with Namco and now 5 years at what is presumably Nintendo's most expensive studio. Which presumably means Nintendo wants the game not only to be a GOTY contender, but also sell many millions and set the stage for it to return as an important franchise for them. But in order to do that, they need to sell not only to the Nintendo die-hard (who would still buy it on the Switch), but to the larger overall so-called hardcore audience. You know, like the general Neogaf crowd. No go look at the typical conversation around the Switch around here. To be blunt, it's despised now for being old and out of date. Bayonetta 3 didn't sell that well. Xenoblade 3 didn't sell as well as XB2. And that was still 2022. What makes anyone think 2024 would be any better?
One can argue Metroid is a bigger franchise, but it really isn't THAT much bigger. And it's exactly the wrong game to try to salvage this holiday season. Like I said, the more hardcore oriented crowd is exiting the stage faster than the more casual crowd. So you would probably want a more casual oriented game like a Mario Party or something. Not only can that franchise survive a weak entry (and let's be honest, this holiday is likely to be Nintendo's weakest in a long time), but it appeals more to the crowd that hasn't already dropped the Switch due to graphics and the like.
And on the flip side, the hardcore crowd are the ones that buy a console day 1 AND are the ones that buy lots of games, so you would likely want multiple games early on that appeal to them. And the hardcore crowd are also the ones who go to social media to talk about games, so getting an early positive impression can help boost the Switch 2's life overall. Getting Prime in early would give Nintendo a huge boost to the hardcore crowd, especially those that might think Mario is too kiddy or whatever (it's been 7 years since Odyssey, another one has got to be out soon). And it would give a huge boost to Metroid itself, possibly breaking out of its 2-3 million sales baseline.
Sure, that's not proof that it will be. But honestly, if it is just Switch 1 only, then it sadly likely means Nintendo is simply sending it out to die.