At today's Fedora Engineering & Steering Committee to discuss the Fedora 21 schedule, per the minutes, Jaroslav Reznik has been tasked with coming up with a provisional schedule that would put the Fedora 21 official release date at 14 October, 2014.
The next Fedora Linux release is being postponed until October since if shipping in August they are left midway between GNOME 3.12 and 3.14. GNOME 3.14 will be released by late September and thus if shipping in mid-to-late October would allow time for a fresh GNOME 3.14 desktop to be incorporated into the release. October/November release targets have also been what's long been sought after by Fedora (among other distributions) for nailing close to the GNOME release time-frame and other software projects.
For Fedora 20 this will mean quite a while until this next release since Fedora 20 shipped last December. At least we might see GNOME 3.12 land in Fedora 20, new kernel upgrades continue to be pushed down to F20, and a Mesa 10 repository is available, all in order to freshen up this release.
The Fedora 21 release is coming late to begin with due to the re-architecting of the distribution at a fundamental level and introducing various new working groups, etc. Other details we know about Fedora 21 at this time is they are looking to drop support for old GPUs, out of the box OpenCL support is being desired, Fedora 21 will likely have Hawkey, and DNF continues to evolve.