I think the PS4 version will only sell 6.5-7m total, but I am not sure we will ever get the final total for the PS4 only version. I find it more likely that this game is going to get ported all over the place: PS5, PC, XB1, Series X, Switch and/or Switch 2, etc.... Once the ports start coming out then they are going to always tell us sales combined across all platforms. Considering that this game is going to get several entries over a long time, it just makes sense to keep porting it to as many platforms as possible. That way the series stays in people's minds while they work on the next installment.
Bonus: I think they will get the last installment out around 2030.
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