So you say but aren't they're all (the latter two) doing their own version of it? Intel with Skylake & Gen9 graphics accelerating apps through OpenCL, Nvidia with Pascal & Power9 working inside an HPC environment. If they're making provisions for it then I see no reason why a given software utilizing OpenCL (or any other suitable programming language) can't make use of preexisting features.
Intel and Nvidia doing something means real business, AMD doing something is usually hot air. There's a massive difference in resource levels from AMD to Intel and a significant one from AMD to Nvidia. So just because these two companies are doing something doesn't mean that AMD should do it, let alone be able to deliver it. In fact, given AMD minute market share on the consumer and server market, it's better for their sake to go along Intel or Nvidia than to develop their own thing.
Of course it isn't but it'll have the same effect that Mantle did, I doubt even you can deny that the latter had a profound impact on DX12, Metal, Vulcan et al.
On DX12? Probably. Microsoft was sitting on DX12 for years because their gaming strategy is totally built around the XBOX, and the Khronos group is too incompetent to move things forward alone (I expect them to adopt Vulcan but fail miserabily on the market, like their always did), but Metal? Apple needs something to replace OpenGL on the iOS, that's not dependent on AMD at all.
And no, HSA won't have the same impact as of DX12 and OpenGL. In this case we have Microsoft actively sabotaging the PC platform as far as gaming is regarded, and the Khronos group is too incompetent to move things forward, so there was actually some interesting low hanging fruits to be taken. HSA is a much tougher nut to crack, as the software companies are too many and their needs too diversed, also there are much heavier hardware IHVs/IDMs to compete against.
Think about it, Mantle, a gaming API, died without a public SDK, probably because the thing was too broken for prime, do you think AMD can muster enough resources to develop something on par with what Microsoft, Intel, Oracle, Nvidia have been trying to push?
AMD has been chasing a lot of rainbows in the last few years, Semi-custom, HSA, Seamicro, Skybridge, ARM, HSA, Mantle, and from these only semi-custom generated fruits in the form of the console chips, and semi-custom is below-par of what they were saying in 2013. Lisa has been slowly bringing AMD back to its sense and killing/leaving to die these distractions and focusing on real, proven markets. I think HSA will eventually find this fate, or at least be severely reduced in terms of scope in order to fit on AMD R&D budget.
AMD financial projections for the next 9 months aren't exactly inspiring, I wouldn't be surprised if we see another round of cuts along with more projects being canned if things don't go that well, and this is a real possibility, given that every single node introduction wreaked havoc on AMD balance sheet in the last 8 years. HSA should be in the forefront in this case.