Most likely Larian want do Baldurs Gate 4 or Bladurs Gate 3 Big story DLC (They spent 6 years on this game/engine. Surely they want to make use of it for more content. Maybe set in Waterdeep or new sword coast locale or heck even Thay or some new setting with new characters). To make a massive Level 1 - Level 16-20 game that spans travel to Waterdeep, Baldurs Gate, Underdark, Thay etc.
Larian kept patching Divinity Original Sin 2 for quite time after it came out on PC on 14 September 2017 and the last "Patch" was nearly 3 years later. Pretty impressive post game support (2 years post release had monthly updates), as Larian was putting game on Switch, PS4, Xbox Series S/X etc.
So its possible Larian try something new and Sven does a big story DLC if enough people ask for it (If BG3 sells well enough like Starfield, then its no brainer to copy Bethseda and release story DLC to keep the artists/programmers/writers all working) for a Level 18-20 cap.
So id expect them to decide on what do 2 years after BG3. Although this time it may go quicker since no Covid is around (Sven confirmed Covid delayed their game by a lot during the recent panel from Hell. So we could have had BG3 in late Q4 2022 or Q2 2023 if Covid never happened. I would not be surprised if Covid ate 6 months - 12 months for their development time due to all the lockdowns, wearing masks, employees or family getting sick etc.
