BlackBerry Curve 8520. So August 5th it is, under a two-month exclusive retail arrangement according to our Walmart-employed tipster. That's the same date T-Mobile will be shipping out its myTouch 3G for those keeping track. That jibes with what looks to be an 8520 "Sneak Preview" pre-launch party kicking off on July 20th and scheduled to run for two weeks. See the invite after the break.
Update: Looks like one has already hit eBay. Thanks, Ben!