It will depend on your model of S20 and whether it is branded or unbranded but in light of the speed at which we have seen the Beta releases coming out, I would have to say that the first stock, stable, releases should be rolling out in a matter of 2-3 weeks barring any hiccups.
[EDIT] With the release of today's 6th Beta only 1 day after the 5th release and the inability to rollback to Android 10, I am guessing that this may be the last Beta build before the stock Android 11 release.