the latest speculation points to December 8th, which is the same date that the Motorola DROID 4 is supposed to be released. But with launch dates for the SCH-i515 all over the place, we wouldn't bet our lives on being able to walk into a Verizon store and pick up the phone on December 8th.
On the other hand, if the Best Buy screenshot is legit, we have at least some idea when the Samsung GALAXY Nexus will be available. Some of the specs on the screenshot, like the weight and the size of the phone, don't match up with the official numbers that Google had on its web site. Assuming for a moment that the screenshot is for real, you can pencil in December 11th as the date when you can go in to your local Best Buy and hound them about the phone, telling them that you know they have it in the back room. Either they will sell you a unit just to get rid of you, or they will call security and have you removed from the store.