Ruin Explorer
Legend
I don't think it's heresy. I think most people who played BG3 and enjoyed it would prefer a D&D game set somewhere else rather than in exactly the same place.Heresy time: Although I understand the value of the brand name, I'd rather they show us something new/new in the 21st century. Have BG4 be a sequel to Icewind Dale or Neverwinter Nights or something.
Visit multiple cities along the Sword Coast. Visit the Dalelands. Those are still pretty vanilla -- which is probably the safest way to go, commercially -- but would incorporate a wider variety of flavors and textures.
Alternately, if they want to get a little bolder, give us a (better) Underdark-driven campaign. Intrigue amongst the drow, where the consequences for a bad social roll can be very serious would be appealing.
As an aside, if one bad roll with 5E's high RNG has very bad-seeming consequences, all you're going to do is make most people save-and-load a lot. Giving people dramatic choices that they own, rather than making them get screwed by dice, is much more effective in this kind of game. Like, you'd already have to have knowingly put yourself in a very risky but potentially rewarding position where you were relying on one or two rolls going right. I don't think they could do Lolthian Drow though because WotC would never approve the wildly sexist society being a protagonist thing.