I think I am hearing they are doing lots of Sun Valley testing internally now so we can get it Jan-March time (as apparantly by March the bulk of it they want ready for FC = feature complete)
There Are Two Versions, Which is the New One? - Windows 10 Insider Preview 20277.1 (fe_Release) amd64 - Windows 10 Insider Preview 21277.1000 (rs_Prerelease) amd64
Apparently only 'seekers' get 21277, so you have to go into Update and opt to install it. But once installed, you cannot go back to the 202xx ones.