Baldur's Gate 3 will be receiving another update in the near future, and developer Larian Studios has some ground rules for players in a bid to help them keep their save data.
Since Patch 3 is "just around the corner," as Larian announced in a recent post to its Steam page, it will bring save incompatibility. Anyone who updates to Patch 3 will no longer be able to play their current save. That's certainly unfortunate, but it should be noted that the update isn't mandatory, so users won't be losing their games left and right.
You can avoid receiving the new update at present by opting out in Steam. Change up your beta branch by clicking on Baldur's Gate 3 in your Steam library, then closing the Betas tab, then opting for "patch2." Even when Patch 3 is released, your game will work on the pre-Patch 3 version instead until you shift over the beta branch to the newest version of the game.
"You can already move to the beta branch now, if you’d like to protect your save file and continue on the current version," Larian says. "Note: save files are not ‘deleted’ from your computer; they’ll remain in your folder, but you’ll only be able to load saves specific to their respective versions."
Additionally, you can turn off automatic updates for Baldur's Gate 3 to ensure nothing falls through the cracks. You'll never receive the update, so there shouldn't be anything to worry about. That way you can continue playing in bliss for the foreseeable future.
Should you accidentally update, don't freak out. Just go back into the Steam beta branch and change it back to the previous version. Hopefully you can do so before the damage is done. Be vigilant, and this shouldn't be an issue for those ready to see what Patch 3 has in store for them soon.