As I said, I might be wrong. But overall I strongly believe people, especially on forums like this, overhype the game to extremes. Don't get me wrong, I'm sure the game will sell well. just look at the EA. But I don't think it will reach that far outside the common rpg market. And that's ok. It's not a niche market.
Believe it or not, but yesterday I discovered that a friend of mine, a person that spends atleast 8hours a day gaming, and has done so the last 17 years, had never even heard about Baldur's Gate. or neverwinter, or icewind dale, or any similar crpgs. Because he simply don't like that genre. But you can be damned sure he keeps tag on every single little news he can find about up coming games that does interest him.
So 50% of players have heard of Baldur's Gate? RPGs might not do Call of Duty numbers, but they're still a significant segment of PC gaming, add to that the renaissance D&D has been enjoying with 5e and you'll find the decision to make Baldur's Gate 3 now was not arbitrary.