Windows 10 will be a free upgrade for “genuine and non-genuine” users
 

Speaking to Reuters from the WinHEC conference in China, Microsoft's operating system chief Terry Myerson said, "We are upgrading all qualified PCs, genuine and non-genuine, to Windows 10." This means that everyone running Windows 7 or 8.1, irrespective of whether you pirated the operating system or not, will be allowed to upgrade to a legitimate version of Windows 10.

It isn't clear if Myerson's comments only pertain to China, or to all Windows users worldwide. We have reached out to Microsoft for clarification, but haven't yet heard back. Myerson's wording certainly sounds like this will affect all Windows users worldwide.

http://arstechnica.com/information-t...genuine-users/

read the small mention though that he's maybe talking about illegal versions in China.