Still some shadows looming over these rumours.
If it downloads and installs automatically, for Beta testers, I m have to assume that the beta tester/user will, in fact, be using Windows 10 at the time. - No big deal there.
Alternatively, in spite of being a Beta tester (5 million currently), if you are using Windows 7 or Windows 8, you will be offered the download in the normal way.???