"Remember the job postings on the Microsoft Careers website I said I would be referencing? You guessed it; now is that time! Here, we have two job postings seeking to fulfill different positions on the same Office team. Both ads make reference to the Office Mobile suite and hint at additional functionality being planned for Office 15. Clearly not going anywhere, Microsoft acknowledges the need for Office tools on mobile devices and they're obviously positioning themselves to meet that need as best they can through the Office 15 time frame (albeit, specifically on their mobile OS platform)"
Just don't look for this anytime soon. The clues all point to around 2013 as the launch, possibly in conjunction with the full Office 15 suite as well as Windows 8 - which probably means we're also looking at Windows Phone 8 as the base OS as well. There are glimmerings of some major changes in store for Office 15 (bye-bye, ribbon UI?), but how much of that will filter down into the mobile version is anybody's guess at this point (and I'd wager that goes for Microsoft too).