Why on earth would you want more content without increasing level cap? I already ran around lvl 12 for the last 20 hours.
Powercreep is bs. Githaynkai powers already make you op. Add consequence to using them and you can actually have power scaling that makes sense.
It's the semi-official concern given as a reason why level cap is 12 and why having DLC for BG3 is hard by Larian.
Personally, knowing D&D 5e. I don't see much of a problem up to and including level 19 (level 20 is ultra hard, because of "fun" things like "Wish", which is almost impossible to properly implement without an omniscient AI as game master / narrator), but I'm not a professional game designer.