Windows 10 will be available for Raspberry Pi 2 for free. I guess this means we are going to see a version of Windows RT especially fitted for Raspi computer. Odd enough Microsoft won't support company's own Surface 2 anymore.
Canonical Ltd (a company behind Ubuntu Linux) is already out there offering Snappy Ubuntu Core for Raspberry Pi 2. Before this Ubuntu has not been available for Raspi. Download Snappy Ubuntu Core for Raspberry Pi here.
Both operating systems (Windows 10 and Snappy Ubuntu Core) are for developers who can create IoT/Cloud projects on Raspberry Pi 2.