According to Paul Thurrott, the biggest announcement Microsoft will make at the BUILD developer conference in April will be its vision for the next version of Windows. Currently codenamed Threshold, the Windows update will likely be called “Windows 9” in order to distance it from Windows 8, which isn’t doing as well as Microsoft had hoped.
Thurrott says that Microsoft will put out three preview versions of Windows 9 before releasing the final product in 2015. The final version will likely focus on improving how Metro-style apps operate.