May with TotK is the boring answer that makes sense after TP and BotW, but the scenario of launching before TotK is an interesting one. While there's not a lot that can generate interest quite like Zelda, the Switch being incredibly popular means there's a lot more people who'd be willing to play it on last-gen hardware than there were people playing TP on GCN or BotW on Wii U, so it might not be the ace in the hole we'd all expect.
I think the Prime remake or another unannounced game makes more sense here than Pikmin 4. Nintendo wants to sell this to people who own a Switch, and Pikmin 4 would be another cross-gen title like Zelda. If the Prime remake is exclusive, it would be an opportunity for a graphical showcase that gets compared to a GameCube game as opposed to a Switch game, which can help further emphasize the system's capabilities. Metroid is enough of a core title that its sales wouldn't be significantly impacted by a low user base at launch, thus letting Nintendo save the likes of Mario for later in the year, when their hardware is more readily available.
It definitely won't be exclusive tho. The game finished development late 2021 and was being developed since 2017. Also all the insiders that talked about it talked about it being a Switch game.
The game can both be a showcase of the new hardware and come to the current one. I mean most games that "wow" people coming since 2020 for PS5/XBS are also playable on PS4/XBO. And they are showcases of what the new hardware can do.
Metroid Prime Remastered will be a showcase of both current Switch and Drake Switch. It'll definitely look stunning (and so will MP4). Both will have enhancements for the new model, probably like HDR/RTX added, 4K through DLSS, etc. God of War Ragnarok is gonna be the biggest release by Sony this year and it's cross gen.
The best example of this is BotW itself. It was a launch title of Switch, while being a Wii U game, and was definitely a marquee experience to have a modern day game graphically that's open world, giant in scope and playable on a handheld!! Twilight Princess was literally the same thing as Game Cube but had some motion controls on Wii and it did wonderfully as its launch title(not as much as Wii Sports tho).
I don't see the next hardware getting first party exclusives as soon as next year, moreso because we have Nintendo titles packing H1, a presumably further in 2023 game(Pikmin 4) and also Metroid Prime 4 that whenever comes will come to Switch too.
There's the games we know are in development for a looooong time that will probably fall in 2023/2024 too and those are Switch games given the time they started development (talking about the next games by EPD Tokyo and 10). I think TotK, Splatoon 3 and Super Mario 3D Next all started their full development about the same time, which was also later than we all predicted, and they're coming (Splatoon came first, Zelda next, probably 2D Mario, 3D Mario and DK over 2023/2024).
Several Switch first party games started development or left pre production and entered full development/made mass hirings in 2019, COVID happened, so that's why we're seeing then over 2022-2024.