Maybe "RT" is for "restart time," as in a legacy-app-free and app-store-based version of Windows with a new user experience and a new version of Office (bundled, albeit with only one new Office app,
OneNote for Windows 8, fully optimized for the new not-called-Metro user experience model). RT's consumer success will in part come down to support from other vendors; e.g., if there is no iTunes client for Windows RT tablets, that will be a big blocker for many people. (Check the link below for more Windows RT analysis.)
"Windows RT doesn’t have Win8′s split personality. It’s aimed directly at the tablet sweet spot — the iPad. If Metro apps rise to the same quality and appeal of the iPad’s built-in apps (a huge “if” at this point), Microsoft should do well in the consumer market. Then it’s only a matter of time before Windows RT tablets move into business, as users haul their shiny new machines to the workplace and demand “bring your own device” support. If that eventually leads to corporate sales, Microsoft has a huge win."
Where we’re all headed with Windows RT