I haven't got the notification yet. Neither on Windows 7 nor on the 10 Insider Preview.
Microsoft just announced that Windows 10 will be available as a download for current Windows 7 and Windows 8 on July 29. For details, see http://blogs.windows.com/bloggingwindows/2015/06/01/hello-world-windows-10-available-on-july-29/
You can already make a reservation, meaning you'll get a mail on July 29 to help you remember to download it.