The Fedora developers have decided to adopt GCC 6 for Fedora 24, but this means that a lot of packages need to be recompiled.
The official announcement:
“GCC 6 is currently in stage3, will move to stage4 around mid-January, in prerelease state with only regression bugfixes and documentation fixes allowed. The release will happen probably in the middle of April. We are working on scratch GCC RPMs and will perform a test mass rebuild,”
The Fedora 24 development will start at the end of January, the Alpha 1 release will be ready by March 1, 2016, the first Beta should come and April 12 and the final system is scheduled for release on May 17, but the Fedora developers have the habit of delaying the system’s release.