Unless something comes up, I don't see a reason why the RC2 release shouldn't be the 1.20 release.
One bug that was fixed since the RC2 release is Bug 40641 - "Links to COPYING and CREDITS on Special:Version should not trigger a download dialog"
There is a work-around for this, though, so I'm not sure it *needs* to be in 1.20.
Since someone at WMF still needs to make the official release, I guess all that is left is to ask Sam to make an announcement. We can just squeeze the release into October.
Mark.