http://en.cppreference.com/w/cpp/compiler_support
Good reference if anyone would like to look into the support by various compilers. Most likely we won't break support for 4.7, and might for 2013, so it would mostly just be the official limits and if we do break them, too bad :P
GCC 4.8 is however missing some C++11 Library support (regex) but I'm not sure we'd really make use of that.
The stuff still missing in 2015 is some rather complex language stuff that no one would probably actually use :P (fancy template stuff and some other stuff)