The closure of the Apple online store is typically used to herald the announcement of new products available for sale.
Apple is expected to announce the iPhone 5 today in an event that is currently taking place, although the device is not expected to be available immediately. However, it could be that Apple will be taking pre-orders from today with the intention of delivering at a later date.
Apple could also be announcing other products today as well as the iPhone 5. The company is expected to launch iOS 5, iCloud, and possibly new iPods.
Predominantly though we expect it to be the iPhone 5 pre-order scheme.