Tesla started rolling out version 2021.4.12 the week of 3/15/2021, and my Model 3 SR+ got it on March 19th. According to the Release Notes, the update includes “Minor Cold Weather Improvements and Bug Fixes”.
Since the severe cold weather is probably in the past for this winter, I guess it will be another 9 months or so before I see any weather related improvements. “Bug Fixes” is pretty generic so no telling what those changes are, but bug fixes are always good to see.