I went with 3.5-4 million. I do believe the release window is kind of light right now, Nintendo has been doing a great job marketing the game, and a demo lets quite a few people take a dip without worrying about taking the plunge.
I also think a lot of the changes Nintendo has made this time around make this a much, much more approachable game. Not in a “this game is for casuals” way, but more in a “this is fun, I’ll take the time to learn” way.