Unless Sword and Shield has really expanded the market for the series I’m not too sure it’s going to match any of the mainline instalments. I think 10 million would be a optimistic estimate as the series spin-offs, even the most popular ones, don’t come close in sales numbers.
Also, if you look at the marketing, very little has been given away about the general gameplay beyond a few teaser shots. I’m trying to force myself to hold out and wait to see the reaction because I feel it’s going to turn out as an overhyped and underwhelming disappointment (hope I’m wrong about that though).