There's no evidence of it now but I just heard from a reader who says that a search for the Streak on the Dell website this morning yielded a real product page that included a "soon" message as well as a list of specs, two press shots of the device (one black, the other red), and a price of "from $499." There was also no mention of the home dock being included in the box, and the OS was listed as Android 1.6 w/Dell UX.
He actually didn't know if the product page's existence was old news and was emailing to ask if it had already been discovered, so I believe that his intentions are honest and that's he's not making things up for sport. He said the page was there when he first got to work and seemed genuinely shocked when he checked again (after I told him that it didn't exist for me) to find that it wasn't there anymore. This would be more believable if there were an accompanying screenshot, I know, but there was no reason for him to take one this morning since he had no idea the page would be gone the next time he went to check.
And even if we had a screenshot, it's possible that the information on the product page wasn't final (otherwise MattatDell's tweet about us not being disappointed was quite the lie!); it could've just been a copy-and-paste from the UK site for placeholder purposes, for example. We'll find out the truth "very very soon," in any case, but since it's pretty obvious that Dell isn't saying anything today (maybe they're waiting until tomorrow just to debunk all the July 19th rumors), I thought it was worth mentioning. The "from $499" bit is particularly interesting to me.
Nothing left to do but wait and see how it all pans out.