The big news today is that a fifth release candidate for Fedora 21 was needed, but Fedora 21 was given a GO for the December 9 release. Fedora folks are also talking about a '"Tick-tock" release cadence' for future versions, which would alternate feature releases with "release engineering and QA process and tooling."
A few hours after yesterday's release candidate was announced it was determined that yet another attempt was needed. RC5 was made available in the wee hours this morning. The only real changes between RC4 and RC5 were the versions of python-blivet and pyparted, which were downgraded due to serious bugs.