The Apple Store is currently displaying the "We'll be back" message in numerous different languages, this is typically Apple's way to announce that new products will shortly be available.
Apple is expected to launch a new model of iPhone at an event taking place later today, the iPhone 5 is expected to have a larger screen and run Apple's new iOS 6 operating system. The iOS 6 operating system itself is expected to be available for current iPhone, iPad, and iPod touch owners either today, or within the next few days.
See also: Live feed: Apple iPhone 5 launch event
It may also be the case that Apple launches other new products today, including the iPod touch, nano and shuffle; the Cupertino-based company may also introduce new Mac models and a smaller version of the iPad.