Fedora.Next is bringing lots of changes as the longstanding distribution seeks to effectively remake itself and move forward with greater vigor. When it comes to this next major distribution update, Fedora 21 already has lined up support for non-KMS drivers to be abandoned, other old GPU support removal, out of the box OpenCL support, Wayland support improvements, Hawkey usage, and many other changes, besides simply having updated upstream open-source Linux packages.
It's been known that Fedora 21 won't be released before August, but beyond that the schedule has been up in the air... With Fedora 20 having made it out in late 2013, this is a long time between Fedora releases with its users generally seeing a release about every six months. However, with more of Fedora.Next being agreed upon and the more fundamental changes being implemented, it's getting time to figure out a schedule to commit to shipping.
For those interested Fedora stakeholders, on the Fedora developer mailing list is a help wanted thread in trying to come up with an estimation for the next Fedora release schedule. Stephen Gallagher at Red Hat is just trying to solicit feedback from the major Fedora stakeholders so that FESCo will be able to come up with an adequate schedule. Look for more information in the coming weeks when we should finally have a Fedora 21 release schedule.