I think the Switch will get its own 2D Mario and that could probably hit 20 mill+ ... but after that the list gets small. Maybe the next mainline Pokemon?
BOTW2 will sell a lot, but probably not as much as BOTW1.
Games that come in the 2nd half of the product cycle simply don't have as much of a runway to sell either. Games released in 2021 or 2022 aren't going to have a 4-5 year window to sell.