As I am working on a C++ library that will be released publicly around 2014, I currently have design choices to make. One of the very useful tool that will be released with C++14 is
Update (Oct 2016):
std::optional was not in the final C++14 standard, so it is never available with
-std=c++1y. Instead GCC 4.9 includes
std::experimental::optional which is avilable with
GCC 7 will include
-std=c++1z i.e. C++17.
Original answer (Jun 2013):
It's currently unimplemented, see http://gcc.gnu.org/ml/libstdc++/2013-06/msg00032.html for the status of C++14 features in GCC's trunk.
When it gets implemented depends on when someone volunteers to do the work, so is impossible to predict.
I would expect it will be done for GCC 4.9, which should be released shortly before the C++14 standard, but there are no guarantees. It is unlikely to get added to GCC 4.8 though, as that's already released and unlike GCC 4.9 (i.e. the GCC subversion trunk) the
__cplusplus macro has the same value for
-std=c++1y so for GCC 4.8 there's no way to selectively enable features for