Larian doesn’t have a history of producing traditional DLC, but Larian is now a much bigger studio than before. They have started pre-production on their next project, but until that is in full production, a lot of their staff would be sitting on their hands, not generating revenue, and burning wages.
I think for that reason alone, there is a chance that we get some sort of DLC before Larian’s next game, but we will see.
If not a traditional expansion, maybe something that uses BG3 assets for a smaller scale project, like the canceled Divinity: Fallen Heroes would be appreciated.