Based on the sources, Microsoft is thinking of releasing the new version of Windows (might be called Windows 9) in April 2015. Internally, the next Windows version is codenamed “Threshold”. Not sure if the final product will be using Windows 9 or not.
And from my understanding, there might be an update for the existing Windows 8.1. It might be called Update 1 or GDR 1 and might appear as early as April this year. At the same time, rumors are saying that Windows Phone 8.1 is coming soon (also around April at Build 2014).
I would want to envision Microsoft to bring Windows 9 (or whatever it might call) to be as compatible as the next Windows Phone version. Microsoft has disappointed me since Windows 6.5 and hopefully, they can pull their act properly this time (no more changing of handset when a new version arrives and neglecting the rest of the supporters who bought earlier handsets).
With the recent increase in “official” apps like Instagram and etc, it looks like they are gaining traction on the other OS.