In a keynote address during Microsoft's Build 2012 developer conference, CEO Steve Ballmer demonstrated multiple Windows 8, Windows RT and Windows Phone 8 devices. He told the crowd, “If it’s not clear, we’re all in with Windows 8. Every group at Microsoft has contributed something.”
Later Ballmer announced, “We have an installed 670 million people on Windows 7. Windows 8 takes less resource than Windows 7. Every one of those is a potential Windows upgrade. In the last few days, four million sales have moved in that direction. We don’t know what will happen with the PC market over the next year. I think with Windows 8, we’ll see growth and vitality, but even if it stays flat, there will be 400 million new Windows devices that you can target with your application.”
He reiterated that 400 million devices would run Windows 8 "for sure."
Ballmer ended his talk with an announcement sure to please those in attendance: everyone there would receive a 32GB Microsoft Surface RT with a touch cover.