Microsoft has announced that the final release of the next version of Windows Server will arrive at some point in 2016. However, the company will continue to release new preview versions throughout 2015, with the next preview build due out in the spring, alongside the next version of System Center Configuration Manager.
As we continue to advance the development of these products, we plan to release further previews through the remainder of 2015, with the final release in 2016. Our next preview is planned for the spring of 2015. Windows Server will continue to share the same core technology as Windows and we will continue working together on solutions for our customers. In fact, the next version of System Center Configuration Manager, which delivers support for Windows 10, will ship in a timeframe that aligns with Windows.
Microsoft did not say when in 2016 we would see the new Windows Server. It should also be noted that though the consumer and server versions of Windows are normally released at the same time, it's been indicated that Windows 10 will make its way to consumers at some point in 2015.