There have been several rumors lately that Microsoft would be bringing Office to Apple’s iPad (and possibly to Android tablets as well). Two stories a week apart have each cited internal Microsoft sources claiming that Office for iOS would be releasing in November. The most recent one claimed that the app is nearly ready to be sent off to Apple for approval.

Those rumors – including the release date – have gotten a bit more support today. Citing “a source familiar with Microsoft’s Office sales team,” Business Insider is reporting that Microsoft is planning to announce Office for iPad at the SharePoint Conference in Las Vegas. The conference is scheduled to start on November 12th, which matches the rough timeline of the most recent reports.

Of course, as I’ve said before, the surprise isn’t that Microsoft is launching Office for iPad. The surprise is that it’s taken them so long. The iPad has been gaining tremendous traction in the business world for quite some time, and Office alternatives – including Apple’s own iWork suite – have been on the iPad for ages while Microsoft calmly pretends the iPad doesn’t exist. The iPad release will likely follow the release of the first Windows 8 tablets, which should be coming this fall as well. There are also rumors of an Android version.

Of course, the world of mobile productivity just got a lot more interesting in another way, as well. In fact, had Microsoft not been planning to bring Office to the iPad, you can bet that Google’s acquisition of QuickOffice would have set them on the path to doing so. By buying QuickOffice, arguably the most popular Office alternative for the iPad, Google is making a big jump into the mobile productivity market and firing a shot directly across Microsoft’s bow. That’s not the sort of thing that Microsoft can allow to go unanswered, which means that we may be in for an interesting little arms race in the world of iPad productivity software over the next few months.