Microsoft is in a tough spot: Windows Phones aren't selling well outside of a couple of EU markets and data indicate that neither is Windows 8. Windows RT and Surface tablets have so far been a major disappointment as well. While it's way to early to "count Microsoft out," clearly the company is in trouble as mobile internet access and mobile computing accelerate at the expense of the PC.
There have been persistent rumors that Microsoft was bringing a version of Office to iOS and specifically the iPad. You can use Microsoft's Office 365 cloud-based product on the iPhone or iPad. (I have not.) But the experience will not be as rich as with a native app.
There are two theories about why Office has not come to iOS as a native app: Microsoft won't pay the 30% "tax" to be in the iTunes App Store and, perhaps more significantly, if Office came to the iPad (or Android tablets) it would undermine the sales outlook for Microsoft's own Surface tablets -- currently the only tablet that offers Office.
Microsoft's compromise may be to offer Office 365 through the browser to iPad users. However by not offering a native app it risks ceding the centrality of Office to a range of apps. Offering a native-app Office would potentially cloud the future of its own tablet devices, which may not be so bright anyway.