Based on some of the prior documents, I believe they are:

MACRO-32 (The compiler for VAX assembly), C++, Ada

MACRO-32 works at a lower level than the other languages, and needs to generate assembly directly instead of an IR. The C++ compiler is being replaced by Clang, and the previous VMS releases used Adacore's compilers, so Adacore will need to be convinced to port their compiler to x86 VMS.

Close. Macro-32 on x86 will use a lower-level interface to the same LLVM backend used by the other languages.

Adding more OpenSource to OpenVMS is __NOT__ a good thing. Especially adding it at the compiler level.

Moving to a common back end, especially for BASIC, would be a truly wretched decision. It would also be the final nail in the coffin of the interactive BASIC environment which VAX had and the industry begged for on Alpha. When it to the Itanium (Itanic) hardware we were all too busy begging for a processor that wouldn't combust like Samsung Galaxy or one of those hoverboards.

The interactive BASIC environment wasn't just for students. It provided a great sandbox to test out algorithms quickly, much like today's script kiddies would call a modern IDE.