[a13xb]

C++11 was originally known as C++0x, so C++17 may yet become C++19.

[moomin]

Yes, and C++17 is a big one, which may well slip, while C++14 was a small one, mostly aimed at cleaning up C++11.

[ksherlock]

c++17 is currently known as c++1z.

You can use Clang in C++1z mode with the -std=c++1z option.