Rather than raising the level caps, DLC could include a new origin character, race, subclass, and a new (or expanded) area to explore (within Act 1, 2, or 3) that somehow relates to the origin character. With the work they put into each individual origin character, even adding a new one per DLC would be great.
I agree with the others saying they might not want to go above level 12 -- and I'm fine staying at the current height and just expanding the breadth/width.
Even if there's no DLC released, it appears to be a complete game. Unlike other game studios, that would probably hold back classes, subclasses, races, etc. or monetize each into microtransactions. We're very fortunate Larian doesn't operate the way other large game studios operate.
Whatever their "next thing" turns out to be, if they put the same amount of love into it as they did with BG3, their "next thing" will turn out great and I hope the best for them.
This would be a great way to do it. A couple Durge-esque origins, but with less off-putting stories. They could make an origin you could play however you like, but maybe in Baldur's Gate they owe a lot of money to someone unpleasant, and the player has options to define what that situation is in a number of ways through dialog with companions is the first thing that springs to mind.
Just giving people new ways to role play the story would make an excellent expansion
