Preview at WWDC likely in June, followed by September launch.
iPhone 5 Now Available for Pre-Order
Verizon, AT&T, and Sprint and Apple are now accepting pre-orders for the iPhone 5. U.S. customers can order on Verizon, AT&T or Sprint. Pricing may vary with your upgrade eligibility. Standard prices with 2 years contract are $199 (16GB), $299 (32GB), and $399 (64GB). The iPhone 5 comes in white or black.
Delivery for pre-orders is expected on September 21st. Alternatively, customers will be able to purchase at retail locations on that same date.
Update 12:26 AM: Users are reporting that Apple's site is extremely slow, and even still down for many users. Customers seem to be having more success using the Apple Store app for iOS, although users needing to change carriers can not take advantage of the app. Orders through carrier websites also seem to be moving fairly smoothly in the United States.
Update 12:32 AM: Apple appears to be having difficulties connecting to carrier servers to verify customer information, and is in some cases issuing reservation confirmations. Users with reservations will receive emails once connections to carrier systems have been reestablished, and they will have 24 hours from that point to return to Apple.com and complete their orders.