According to the official PlayStation Blog, the PlayStation Network will be down for scheduled maintenance this Thursday, August 22. Community Manager Paul Sullivan explains in the blog post that the maintenance will start around 12:00 PM PT and most likely end at 6:30 PM PT if all goes well.
The usual will not be available during the maintenance period. PlayStation Store, PlayStation Home and account management will be inaccessible unless you sign in and stay signed in before the maintenance begins.
With this happening during the week of Gamescom, maybe we will get some amazing news when the maintenance period is over. New features, a redesign, or some sort of sale could happen people. More likely is that PSN needs a good scrubbing to clean out some bugs.
Source [PlayStation Blog]