From my various years following cellphones, and other technology confidentiality dates can go months beyond when the device itself is released. Look at Apple with their Iphone, I'm pretty sure for the Iphone 3-4 the agreement went beyond when it was made public and released to retail. It just depends on what type of clauses are on this agreement.
On that note, I really hope it comes out on July 28 or Aug 4th. My wife needs a new phone, and I'm kinda itching to upgrade from my DX. Nothing wrong with my phone, but just want "the latest" but I'm not going to freak out if it's not out by those dates. It's the fun of the chase and leaks.