April 2015, but it's unclear if that was just a good guess, or something connected to this info.The info comes from a leaked document that mentions a couple of interesting things. It labels both Windows 9 and Windows Phone 9 as having planned preview releases in "2015 Q2 - Q3", which is a pretty wide range that could mean anytime from April to September. Unfortunately, there is no word on what features are planned for either of those updates. It does mention that Windows 9 and Windows Phone 9 are already in development though. There had been rumors before claiming that Windows 9 would be coming in
Another interesting note on the leak is that it shows something called "Windows 365" which is also labeled as being in "Alpha based on Windows Core", which was first mentioned about a week ago. The only connection that can be made is to Office 365, which is the subscription-based, cloud-powered version of Office. Microsoft's new CEO Satya Nadella has said that the company will be focusing on its cloud offerings and integrating its products through the cloud, so it shouldn't be a surprise that Windows itself would also be part of that plan. The fact that Windows 365 is "based on Windows Core" makes it sound like an operating system of some sort, but it's unclear what devices it would be for. Still, a subscription-based version of Windows has been rumored before, and this seems to be confirmation.