^Aye, 4.1 (with the 420 shader pack extension which is very likely to be implemented anyway - I haven't checked) maps well enough to DX11. I doubt SE is being bold enough to do this, but one thing they could've tried instead of going for a DX11 client like they've been talking about for a while is simply do a GL4+ client and call that the "DX11 client", potentially reusing work on the OSX version.

While the current state of GL in OSX is more than acceptable for game development (though obviously not ideal), the late adoption of anything over 3.2 likely stalled its expansion as a gaming platform.

I don't know the full story, but Apple's implementation of GL4+ came at a similar time as Intel's implementation for their HD3000/4000/Iris integrated GPUs. I'm willing to bet these two are somehow related.