Why? How do you know this?There's absolutely no chance they won't have at least all the base classes and races.
Ranger class is already confirmed
Even garbage like Sword Coast Legend had basic races and classes. Of course, BG3 will have them all.
And there is that quote from Swen
https://www.pcgamer.com/how-baldurs...-rules-of-the-tabletop-games-theyre-adapting/
"We've done a lot more than people expect, I think," he continues. Still, cuts have to be made. "We made a list of everything that's in the Player's Handbook, and we coded it green, orange, red. Green, meaning [we can use it as-written]. Orange, needs change. Red, impossible—or maybe not impossible, but we'd have to make a completely new game just to support this feature."