Originally BG3 was supposed to cover 1-10 levels. Then it was mentioned that the level cap will be pushed higher, but we don't know how much higher.
Considering how close in many ways BG3 is to Larian's own Divinity: Original Sin series, I don't expect a direct sequel in vein of BG2. Considering how much interest the game generated a sequel is a possibility, but I would expect more in lines of a Larian sequel then direct Bioware sequel. That's how they handled Divinities, and that's how they are handling BG3.
