Based on BGR's claims, it appears Apple will actually be revealing pre-announcement information to a select group of Apple retail staff 12 – 24 hours ahead of a major announcement. This would be a first for Apple, and a bold move from the Cupertino machine. But this may be an Apple litmus test, and if successful may lay the groundwork for how future product launches roll out.
It appears Apple corporate does not trust their retail employees (smart move), in that BRG's source claims the 10-15 employees that will be pulling an all-night-er in the stores, must not only sign an NDA, but also lock their cell phones in the managerial office.
I have worked at an Apple retail store in the past, but any observer walking into an Apple retail store during a software update can attest to it taking a long time to re-image systems. My best guess is Apple will not only be re-imaging OS X Macs, but iPhones and iPod touchs, with a new OS versions that have the hooks to tie into the much rumored iCloud service. North Carolinians may see their lights dim, as Apple's datacenter finally reaches full operational potential. "Fire at will commander!" Sorry, couldn't resist the Star Wars reference...
I originally figured the 10-year retail anniversary would be nothing more than a Black Friday-like event. I no longer believe this is the case. Looking at BRG's information it appears the the retail window display will be swapped out, and the large amount of time these 10 - 15 employees will be working seems to indicate the re-imaging of every type of Mac OS and iOS system in the store, along with training.
New hardware? Doubt it. Jobs and company don't strike me as the 20th Century Mac anniversary edition type. The next 4 - 5 weeks promise a lot of fun in the world of all-things-Apple.