Quote from article, "Beta testers will not automatically receive a free copy of Windows 7. Many beta testers are already subscribers to TechNet; those of you who fit that description will be able to download Windows 7 RTM shortly after RTM happens for free as part of your subscription."
Article link -
When will you get Windows 7 RTM? - Windows 7 Team Blog - The Windows Blog
Article link -
When will you get Windows 7 RTM? - Windows 7 Team Blog - The Windows Blog