The Verge have come up with some interesting news.
Apparently Microsoft will be shipping a Preview version of Office 2013 RT as part of its Windows RT ARM-based tablets later this year. That version will apparently be upgradeable to a final copy in early 2013.
In order to ensure battery life and reliability are not impacted on tablet devices, Microsoft have decided to drop macros, third-party add-ins, and VBA support from the Office 2013 RT edition.
This is all subject to any official confirmation from Microsoft.