I think BG3 will sell 10 million! I think it will sell at least as well as the Dragon Age games if not more.
I agree, I think people are woefully underestimating the potential of this title. The Platform alone is worth buying and if Larian or anyone else builds additional professionally done modules for the platform it would also really spur growth.
The Multiplayer is so fucking good it makes me angry. I want small, self-contained 5-6 hour adventures to do with a group, as well as LONG sprawling stuff that requires multiple sessions.