Microsoft has just announced that Windows will be available on October 26th; the announcement came from Steven Sinofsky at Microsoft's annual sales meeting that customers.
Earlier this month at the Microsoft Worldwide Partner Conference the company said that the platform would ship in late October and that RTM would occur in early August. Now that we have a firm date, we can officially start the countdown timer.
Windows 8 is a massive bet for Microsoft as they are dramatically changing the Windows 8 experience. With their hybrid desktop/tablet OS, Microsoft is building a unified platform across all of its products including Windows Phone and we suspect (but can't confirm) that next generation of Xbox.
Since the general availability of Windows 8 is now known, we also finally have a target date for the Surface RT tablet as Microsoft previously said that it would go sale when Windows 8 launches.
Source: Windows Team Blog