I put it at 13-14m, mostly because I expect them to release another Mario Party on the Switch. I can see it selling more than that though if we are still a few years out on the next Mario Party.
This is only the second Mario Party I've owned, so I like it about as much as the other one (the first one on the Wii, whatever that was).
curl-6 bet me that PS5 + X|S sales would reach 56m before year end 2023 and he was right.
My Bet With curl-6
My Threads:
Master Thread, Game of the Year/Decade
Switch Will Be #1 All Time
Zelda Will Outsell Mario (Achieved)
How Much Will MH Rise sell?
My Bet With Metallox