Both of these are definitely going to sell more than two million. You’re vastly underestimating how huge the Switch install base is right now. TOTK sold 2/3 of BOTW’s lifetime sales in 2 months
It’s time to get out of your “nobody is buying games and everybody wants to move onto Switch 2” bubble. That’s not reality.
You can't use Tears of the Kingdom's data to justify other predictions like that. ToTK is an extremely unique mega game that had Nintendo's complete and undivided attention for marketing and push that as the marquee AAA Nintendo game also just carries enormously different weight and can power through the market to claim the top spot. Something Super Mario Wonder will also be extremely capable of doing.
Mario RPGs are not, and have never been, those kinds of games. They have generally sold well and done admirably for a Mario spinoff, at their best competing alongside a lot of the other top Mario spinoffs not named Mario Kart. The highest achievements of the Mario RPGs as a whole across all their iterations seems to be Super Paper Mario's 4.3 million and Mario & Luigi Bowser's Inside Story at a similar 4.13 million (per a Nintendo 2011 earnings report since that number is a bit less known). Both of which also released on extremely popular machines at the height of their respective dominance as well. That feels like a pretty reasonable ceiling for these games in a best case scenario to me.
Super Mario RPG and especially TTYD are releasing much later in the consoles life than either of those "peak sales" titles came out, both are also going to have a bit of full priced remake doubt to contend with (well I guess we don't
absolutely know TTYD will be full priced, but it seems likely given Nintendo's tendencies), and then both are indeed filling a similar niche in potentially a relatively short time frame. I don't think Nintendo is like sending them out to die or whatever, but I do think those are realities that make them both hitting huge sales numbers a bit more difficult.
And the non huge Switch games definitely have shown this year to be a bit behind. Not to like a detrimental level, just games aren't seeing the same legs that earlier Switch releases saw. XC3 is still behind XC2, Splatoon 3 is behind Splatoon 2, Fire Emblem Engage came in well short of Three Houses, etc. Metroid Prime Remastered people swore up and down would be the new sales juggernaut of the Metroid franchise for it to have sold a very reasonable 1 million plus. I just feel like there's been a huge expectation of crazy sales rather than just grounded good sales because the biggest and most popular evergreens continue to do crazy stuff. Two Mario RPGs crossing 2 million late in the Switch life puts them above literally every other Nintendo released RPG on Switch except for Three Houses and XC2, that would mean something still. And we generally see a lot of drop-off between systems when people begin moving on. Which again, is fine. Samus Returns barely got past half a million despite the 3DS install base when it released deep into the Switch's first year, but it gave Nintendo the results they wanted to send Mercury Steam on to do Dread.
I just don't necessarily agree these games are set up for like the breakaway crazy success beyond what Mario RPGs have done in the past. Excellent sales that encourage Nintendo to keep making Mario RPGs? Absolutely! Breaking through the ceiling of Mario RPGs because of the Switch install base? I'm not sold on that yet but I'd LOOOOOOOOOVE to be wrong specifically on this point. And if I'm predicting one to do it, it's Super Mario RPG because it'll have had a main Switch 1 holiday paired with Wonder to boost it (whereas TTYD might not enjoy the same room to breathe in a situation where it is paired with an upcoming Switch 2).
If we get amiibo for the TTYD remake, how far do you think Nintendo will go? Just Mario? Partners? Bosses?
Considering how conservative and careful Nintendo is currently with Amiibo, probably just Mario himself if they were going this route... And considering they didn't even like use a lot of Amiibo in the past year they could have reprinted, I'm not super convinced Amiibo is as much of a priority for Nintendo these days for Paper Mario to get one, which is very disappointing to me.