At the Fedora 20 Alpha Go/No-Go Meeting #2 that just occurred, it was agreed to Go with the Fedora 20 Alpha by Fedora QA, Release Engineering and Development. Fedora 20 codename “Heisenbug” will be released on Tuesday, September 24, 2013. The final Fedora 20 release will not come earlier than December 6.
This was the second Go/No-Go meeting, as on the first one a date wasn’t decided. Also Fedora 20 final release will slip one week due to unresolved blockers.
You can find the full schedule for the Fedora 20 release, here.