Per the official release schedule, Fedora 21 is expected to see its alpha release on 5 August while next week (22 July) is the software string freeze and the alpha change deadline. Following that alpha release is a planned Fedora 21 Beta on 9 September, final change deadline on 30 September, and hopes to ship Fedora 21 final on 14 October.
In encouraging early testing to hopefully lead to an on-time release of Fedora Linux, which has been seldom accomplished for recent release cycles, the first test candidate of Fedora 21 Alpha is available for those wishing to try out this latest Fedora distribution on non-production machines.
F21a-TC1 can be downloaded from FedoraProject.org and again is only recommended for those wishing to help with early smoke testing of the next version of Fedora. More Fedora 21 tests and coverage will occur on Phoronix when the official release is in range. Fedora 21 is bringing with it many changes and new features.