A posting to the LLVM blog on Sunday confirms the C++11 support being officially complete. The new features to be found in the upcoming LLVM/Clang 3.3 release include support for C++11's [[attribute]] syntax, support for inheiriting constructors, thread_local variables, and much more.
While C++11 support is now officially complete, developers have already begun work on likely features for C++1y, the next revision to the C++ language. C++1y is also known as "C++14" as it's likely this language update will be ready in 2014.
New work here includes generalized lambdas, return type deduction for functions, a more powerful constexpr feature, and more. Work on these features were prototyped within Clang even before standardization and that the implementation of these features should land in the code-base in the coming weeks. Taking advantage of the unreleased C++14/C++1y support can be done by passing -std=c++1y to Clang.
Already within Clang for C++1y/C++14 is also binary literals, partial support for run-time-sized arrays with automatic storage duration, partial support for clarifying memory allocation, and member initializers and aggregates.
Other talked about features include file system and networking libraries as well as a simplified concepts implementation. Other proposed features are covered within this article from earlier in the month.
The C++ support status continues to be documented on this web-page.