One good multicore programming language has been in production use for decades, and is in heavy production use by parallel-naive developers, whom it enables to keep large parallel systems usefully busy.
A huge amount of scientific code is written in Matlab. If someone manages to do a good job of automatically parallelizing Matlab, it will certainly qualify as a good multicore programming language.
I am sorry if you were expecting something high-minded, but then again good multicore programming languages are not about high-mindedness. They are about enabling people to get their jobs done in the work-a-day world.