There are reports that Microsoft is giving final touches to a touch based version of Microsoft Office for iPad and there is every likelihood that Microsoft Office for iPad will come before it is released for Windows based tablets.
It is likely that this will be released as a downloadable subscription based app at around middle of this year.
There have been long discussions about making Office available for tablets. While the subscription based Office is available for home users and business users for desktops and notebooks, no version for tablets is available as yet. Different version of Microsoft Office suite are also available for iPhone and android and Windows phone smartphones.
It is not likely that the office for iPad will hit at the Windows-Office relationship because Office for Mac has been available for so many years and it has added only to the profitability of Office.