HP's Stephen DeWitt at the Engadget Show has made an official announcement:
July 17th is the Official retail launch where you will see promotions, bundles and advertising of webOS products and HP´s PCs, as well.
What can we expect for the 17th?
That's our official retail launch date. What you're gonna see is all of the major retailers will have their advertising and their promotions. This weekend is really the beginning of the month-long back to school season. We very consciously picked this as a launch date. Look for major promotional activities, broadly. Not only across all of our webOS devices, but across our PC products as well. Look for a lot of in-store experiences: merchandising, labor, promotions, bundles -- all sorts of things will kick off on the 17th.