To be fair, HPC guys are pretty willing to use new platforms even if they have to recompile and tune their own software and the HW is a bit buggy.
Two key obstacles for ARM remain, their 64 bit chips will need:
1) leadership FLOPs/W and FLOPs/$ to woo any of the HPC world away from x86. 2) a world class optimizing compiler.
That is the best case scenario. The typical scenario in the server market are no-nonsense IT folks who want utterly reliable proven hardware with a ton of off-the-shelf apps. Good luck getting traction with those folks ARM and friends.