I believe nVidia has a similar effort going (can't remember the name), so it's still not a single agreed standard, but it's moving in that direction I feel.
nVidia's PTX is the most similar thing I can think of (and I know nVidia's GPGPU products pretty well right now). PTX is an ISA for a virtual machine, which makes it similar to HSAIL. PTX doesn't come with a memory model specification though.
However, I don't think either HSA or PTX is very important if nVidia, AMD, and Intel (wrt Xeon Phi's) don't start agreeing on standards. I haven't seen anything to convince me that nVidia wants to work within standards, and CUDA seems to have most of the market share right now, so I'm not too hopefully for portable heterogeneous computing in the near future.
To my grandparent poster: I don't think working with GPUs is that bad right now if you bind yourself to a vendor. In my experience, drinking the CUDA kool-aid (CU-aid?) isn't all that bad.
I believe nVidia has a similar effort going (can't remember the name), so it's still not a single agreed standard, but it's moving in that direction I feel.