Ballpark of 25M I think for NSW version. It's trending to be at around 20M by the holidays next year and this is at a $60 MSRP (in the US Walmart/Amazon have been selling at $50 for the last 6 months or so but in JP I think its one of the higher priced NSW titles). A discounted "Nintendo Selects" (or whatever the NSW equivalent may be) version down the line is going to help as well. I don't think the sequel is really going to affect its legs negatively - OTOH it just brings the spotlight back around once its releases.
The real big deal is that it is a single-player game with no online features legging out like this. That just doesn't happen - Skyrim is the only other performer like this in recent years and its legs are boosted by 4 different releases (OG/HD/VR/NSW). All other monster leggy sellers have major multiplayer/online/both functionality (Wii Sports/MK Series/GTAV/Minecraft/PUBG).
Nintendo's captured this phenomena twice before (huge leggy SP run) - SMB in the 80s and Pokemon RGBY in the 90s. Only fitting that their #3 finally get its moment as well - the difference being that those games basically started the franchises, whereas Zelda's having its moment 3 decades later (though of course Mario was a thing prior to SMB).
As long as they hit the right cues with BOTW2 marketing, I think that is going to have a massive Pokemon/SSBU level launch. BOTW's legs are essentially the result of best/near-best of all time WOM - exactly the kind of thing that carries over into a sequel's opening.
NSW HW & Evergreens Quarterly Shipments
NSW HW & Evergreens Calendar Year Shipments
