Note that gcc's C++11 support was feature-complete as of about two weeks ago... :]
[Seriously]
[Seriously]
If Clang is feature complete, compiler and library, and GCC takes ~N years more to be feature complete, compiler and library, then Clang could win. People might say, "I'm tired of not being able to use feature X, it's been implemented in Clang for two years", drop GCC, and install Clang.