In a headline, with no body text, over at the Microsoft News Center, a press release is announcing that the Windows 10 Anniversary Update will be available on August 2nd. We've been expecting the update in late July, but this date is close. (updated to remove hasty calendar mangling)
Obviously someone hit publish before they were supposed to, as there's nothing to the press release but the headline, and there's no telling if the August 2nd date is final, but it is an official Microsoft "document," so there's that:
We'll have more, of course, once the details have been filled in.
Update: Microsoft has made it official with a full blog post.