C++14/C++1y should be officially released this year as a small update over C++11, for which LLVM/Clang (and GCC) already have decent support. In fact, with the current Clang 3.4 stable release all of the key C++11 functionality should be in place.
Developers have begun working out very early support for likely C++1z features that are already being proposed. Among the features already in the Clang SVN code-base for the Clang 3.5 release this August include: static_assert with no message (N3928), disabling trigraph expansion by default (N3981), terse range-based for loops (N3994), and typename in a template template parameter (N4051).
Of course, many other features will be added to the C++1z feature over the next three years, but this is a good start that will begin with LLVM/Clang 3.5. The Clang online documentation has been updated to begin reflecting the C++1z support with the Clang C++ status page.