Microsoft has not revealed all the details about pricing for Windows 10 yet, but they did announce that Windows 10 will be free for the first year to all Windows 7, Windows 8.1 and Phone 8.1 users.
Wow, thats cool, but does that mean, I will have to pay for Windows 10 after the first year?
No. Its a promotion to get as many users to upgrade their existing Windows 7 PCs and Windows 8.1 devices to Windows 10. As Microsoft Program Manager for Windows Terry Myerson described it:
This is more than a one-time upgrade: once a Windows device is upgraded to Windows 10, we will continue to keep it current for the supported lifetime of the device
–at no additional charge.
As in the past, we will offer different Windows editions that are tailored for various device families and uses. These different editions address specific needs of our various customers, from consumers to small businesses to the largest enterprises.