Prolific Phoronix Forums contributor and AMD employee, John Bridgman, has been making some HSA Linux comments in this thread. Bridgman noted, "For HSA on Kaveri we're aiming to have everything finished and open in 2014, although opening the Finalizer may drag on past that."
AMD's open-source OpenCL support has been lagging behind the proprietary drivers, but Bridgman says they're trying to improve upon that too. In particular, it seems they may try to open-source more of their proprietary OpenCL driver implementation. Bridgman said, "For OpenCL not sure yet -- we're trying to get more people working on it and open up more code from our proprietary implementation, so rate of progress should improve but I don't know how much yet."
The open-source HSA Linux support will primarily benefit Kaveri APUs and future AMD architectures.