The thing is, pre-orders are absolutely insane for this version, it's releasing around the same time as a YW movie that already broke multiple records regarding pre-ticket sales and it's the holidays. It seems the craze wasn't even at its peak when the original YW2 launched.
I don't think it's going to get a 2 mil opening (although that would be amazing), but it's obviously going to sell very very well.
I have no doubt it'll do well, but do note that Pokémon and Youkai Watch sold the amount they did at least in part due to multiple versions and people buying multiple versions. It's a large reason why Pokémon's enhanced versions never sell anywhere near the same as the originals.