Arm Working On Clang C++ For OpenCL 2021 (OpenCL 3.0 Compatible)
They are pursuing "C++ for OpenCL 2021" as the C++ equivalent to OpenCL 3.0.
Pending upstream with The Khronos Group is also the C++ for OpenCL 2021 draft -- also being organized by Arm.
The C++ for OpenCL 2021 is intended to be backwards compatible with OpenCL C 3.0. This new support in Clang shouldn't be much of a challenge with OpenCL 3.0 being mostly about making OpenCL 2.0 features optional and Clang already having good CL2 support plus all of the OpenCL 3.0 C support that's been worked on to this point.
Those interested in this C++ for OpenCL 2021 work being organized by Arm can be seen via this mailing list post.