"Going by word on the grapevine, Samsung has once again postponed the rollout of the One UI 4.0 beta. Initial reports indicated a September release, starting with the Galaxy S21 series, but that will no longer be the case. The One UI 4.0 beta has supposedly been postponed, with Samsung choosing to spend some more time on bug-fixing instead. It looks likely that the beta will finally start rolling out in October."
This could postpone a stable release until December or early January.