Today our kernel compilers don't natively support C++ kernels. However, because we do support SPIR and SPIR-V this does leave the option that a 3rd party tool could compile another kernel language (including one with C++ features) to these intermediate languages. This isn't exactly the same as native kernel C++ since things like debugging and performance analysis are more indirect but may be at least part of what you are looking for.
More info on Intel SPIR/SPIR-V:
These may be of interest for C++:
Just to set expectations, we're very interested in these new directions but our current scope is the components enabling SPIR/SPIR-V and below in the stack. You will get more details, issue support, etc. for 3rd party tools compiling to SPIR/SPIR-V by working with those projects directly.