If you’ve played around with Windows Server 2012 you’ll have noticed that Windows Deployment Services supports ARM as an architecture, just as it supports x86 and x64. If you’ve had a look at the categories for WSUS, you’ll notice that Windows RT is listed. Windows RT is also listed in the text of a fair number of group policies. The hooks built into Windows Server 2012 hint at the possibility of a domain joinable version of the OS designed for the ARM architecture.
The interesting question is “why isn’t there a Windows RT Enterprise Edition”
Windows RT already has local group policy (don’t believe me, type gpedit.msc into the Search charm) and Windows PowerShell – both things that seem out of place in a purely consumer targeted operating system. Conceptually, PowerShell on RT is a bit like the idea of a Bash shell (OSX command prompt) on an iPad. It’s not ridiculous (iOS and OSX share a common lineage), but Apple probably didn’t include it because they didn’t see the need to provide the target audience with that type of functionality.
My guess is that because it doesn’t run software compiled for x86, idea of Windows RT Enterprise edition has been put on hold. All the bits are in place to “flick the switch” if and when it makes sense. Given that enterprises move slowly adopting new versions of Windows, they’d be even slower to adopt a new OS architecture.
My guess is that we will see a domain joinable version of Windows RT in the future at some point, but that there’s probably little need for it until Windows 8 gets enough market share to have application developers get serious about publishing to the Windows Store (because Windows Store apps run on x86, x64 and ARM).
ARM better meets the long term usage case for laptops – it keeps things light and it offers substantial power savings. In the long run the light laptop with the long battery life is going to be the one you choose to carry about over the heavier laptop with the shorter battery life. There is a need for an OS that runs on ARM that can also be managed in the way that a traditional Windows client desktop can be managed. That need might not be strong at the moment, but Windows RT is well positioned to meet that need as it develops.