All three major OS publishers, Google, Microsoft and Apple, are likely to have plans to combine both their mobile and desktop offerings.
Although there has been no official announcement from any camp, there have been hints like the tighter integration of cloud components, the adoption of marketplaces and stores, and better integration with their respective mobile devices. I therefore believe that Mac OS X 11, Windows 9 and Google Android 5 will almost certainly all be deployed on desktop and mobile devices. That's a high risk bet but I'm making it.
And because Apple charges a pittance for Mac OS X Mountain Lion (£13.99), it would make sense to deliver a mobile/desktop version of OS X for free given that Apple doesn't charge for updates to iOS. Apple already gives Mac OS X Mountain Lion for free to customers who purchased a new Mac after 10 June.
A first glance look at the features offered by Mac OS X Mountain Lion shows a concerted adoption of many mobile features that first appeared on iOS.