Clang appears to be following the same path that WebKit has. Apple switched over to Clang years ago and the pace of development of Objective-C accelerated immediately. A few years ago Clang became the default compiler for FreeBSD, displacing GCC. In early May Microsoft announced that they’re Bringing Clang to Windows. According to The Register, Microsoft will have a release of Visual Studio that uses Clang as the front-end to their compiler in November.
So then the next question is whether Microsoft will feel the need to fork Clang, as Google did with WebKit.