Citing "sources familiar with the company's plans," Tom Warren at the Verge reports that Microsoft will ship the first batch of Windows RT-powered Surface tablets with a paired-down version of Office 2013 RT.
Among the stripped-out features are "macros, third-party add-ins, and VBA support," and a "'small number of other features," says the Verge's source, who also says you will be able to upgrade to a fully featured version of Office 2013 RT in early 2013. Microsoft has already announced that Office 2013 will be included with all Windows RT-powered devices.
We have contacted Microsoft for further comment, and will update this post when we learn more.
Update: Asked to confirm an earlier Microsoft press release, which states that "Office Home and Student 2013 RT...will be included on ARM-based Windows 8 devices, including Microsoft Surface," a Microsoft spokesperson responded, "that is accurate, but we have not disclosed specific packaging details beyond what is in the press release."