Recently Microsoft merged developer accounts across the two platforms such that if a developer had an account to create and publish apps for Windows 8, they now also have an account for Windows Phone 8, and vice-versa.
Yet, apps are still distinct; unlike Apple's iOS, there is no concept of a "universal" app for Windows at this time, although it is generally expected Microsoft is heading that direction.
Meanwhile, Mark Shuttleworth, founder of Canonical, states Ubuntu Linux will achieve full convergence before Microsoft.
Shuttleworth announced that Canonical is working to unite the code base for all its Ubuntu variations over desktops, mobile phones, televisions and even its server incarnation. This goes further than Microsoft would, with any merger of Windows Server and Windows desktop operating systems being extremely improbable and unlikely.
Ubuntu is still continuing to target major releases in April and October as it always has done, but Shuttleworth doesn't see convergence happening in version 14.04, suggesting it could be achieved in versions 14.10 or 15.04. In either case, he still expects this to predate Microsoft achieving the same thing across Windows desktop and phone operating systems.