Around which time Firefox is intending to make the same changes, having deprecated v2 manifests (this post seems to use that term to mean the actual removal) and doing all the API swaps to service workers and the such. Firefox just makes all the same decisions Chrome does, the good and the bad.
Mozilla does plan to support the old request-blocking APIs indefinitely, though, even after the Manifest v3 switch, until an alternative that meets the needs of extension developers is developed.
https://blog.mozilla.org/addons/2021/05/27/manifest-v3-updat...