This is all speculation.
I suspect that parents who have played a mario game, and those that watched the movie this year, will be buying the game for the holiday season. If the Mario Movie made approx. $1.36 billion and a ticket is approx. $10 (this is a guestimate based on the economy in America and decline of other currencies), then 136 million people saw the movie. If they enjoyed the movie and honestly most people I've talked to did, then we can assume that maybe 35% are interested in the game giving us a minimum total of 47.6 million. Mario Wonder has sold approx 5 million as of now (maybe near 6), and these are the hard core fans that buy games because its new and exciting.
I am not counting these 6 million with the potential 47.6 million who might be interested in the game for these 6 million hard core fans were going to buy the game regardless.
So based on my random logic Super Mario Bros. Wonder could very much so sell 50 million units. Yes it is on the end of the Switch's lifecycle but that just means the audience is much bigger. 2-D Mario games are always evergreen titles, and it will continue to sell even into the next consoles lifecycle (maybe even 2 years into it).
Sorry for lack of quotes and other facts but I just want to let people know that I agree with OP.
Lifetime Sales Predictions
Switch: 160 million (was 120 million, then 140 million, then 150 million)
PS5: 130 million (was 124 million)
Xbox Series X/S: 54 million (was 60 million, then 57 million)
"The way to accomplish great things, is to be indefatigable and never rest till the thing is accomplished." - Joseph Smith Jr.
