Earlier quoted context omitted.
"but I don't see how an architecture that deviates significantly from the x86 norm could gain traction in this Windows world." One possible way is that Linux quickly adapts to support it and gains a significant, un-ignorable performance advantage on the server side, forcing MS to step up and quickly support it as well. Basically, similar to happened with the transition to 64bit, must moreso.
With AMD's support for GPUs under open-source? Their lack of support in the past (to the point of not even properly documenting their hardware) is not very encouraging.
The real issue at hand is that the open source drivers are incredibly horrid. It's hard to write drivers, surprise!