TechCrunch is reporting a widespread rumor that the iMac may be updated to include iOS within the next 60 days. Word is that it will run a traditional OS X install, and will also allow users to activate "touch screen mode," launching them into iOS.
This makes sense for several reasons. Apple recently changed the name of their "mobile" OS from iPhone OS to iOS, effectively removing the inherent notion that it is strictly a mobile OS. Also, Steve Jobs was recently quoted saying that Apple has no plans to introduce an App Store for OS X, and with iOS on the desktop, they may not need to.
There are also reasons for which this rumor seems rather suspect. Capacitive touchscreens are commonplace in the mobile sector, but producing capacitive touchscreens at 20+ inch sizes is something that has yet to be seen. The economics of producing such large versions may not yet be feasible.
Either way, it is an interesting prospect, and it would be a great way for Apple to test the waters of a simplified touch OS in the desktop space.