Going back for many months we have known that FreeBSD developers (and BSD users in general) have been pushing for a LLVM/Clang world and to limit the usage of GCC. Clang has grown in functionality for being on-par with GCC as a C/C++ compiler and it's more liberally licensed than the GPLv3 GCC and the LLVM-based feature-set continues to expand like faster and lighter compilations. This has been part of the plan for FreeBSD 10.
For nearly one year in the FreeBSD "head" state for FreeBSD 10, Clang has been the default x86 compiler over GCC. Clang is their future. The change made to the latest FreeBSD 10 state as of 7 September is that GCC and the libstdc++ C++ standard library are no longer built by default on platforms where Clang is the system compiler.
Up to now GCC was still part of the FreeBSD base system, but for architectures where Clang is being used -- including x86 and x86_64/amd64 -- GCC is being wiped out. This also includes removing libstdc++ as FreeBSD is using LLVM's libc++ library. Those wanting to still keep GCC on their system to live alongside Clang will need to set WITH_GCC and WITH_GNUCXX in their src.conf.
Other interesting features of FreeBSD 10 are covered in this article. FreeBSD 10 will likely be released in 2014 while developers are currently working on the belated FreeBSD 9.2 update.