I personally think I'd enjoy whatever BG3 becomes in the end. The question is exactly how much I would.
My REAL worry is that, assuming the current status quo doesn't really change... BG3 takes off enough that most future DnD games attribute its success to how the combat mechanics and encounters are designed, and take many of the same design lessons from it, if not outright borrow the same engine (when everyone praises the cinematics and writing/reactivity, but the combat design straight up splits the community at this point).
Such an outcome would be completely horrifying, as future DnD games should not be based on a template that's outright missing proper reactions for one. The gaming industry is historically awful at really understanding why certain things are popular, and fail in trying to emulate success.
I guess that's a little bit of a minor concern. It is unlikely. You are forgetting one important thing and the subsequent D&D games don't even have to be RPGs. You don't even have to look far. Dark Alliance is the best example of this, the game doesn't even pretend to follow the rules, and this is a game published by WotC (they probably own the studio too, though in this case I'm not 100% sure).
