iLounge reported that iPhone 5 will still have glass back panel too, just like the iPhone 4S.
(2) Another Glass iPhone. Despite the well-established “aluminum-backed iPhone 5” rumors that have continued to circulate since the iPhone 4 was released, Apple is nonetheless continuing to experiment with glass and ceramic rear shells for a future iPhone model. The upshot is that the new design would be like the iPhone 4, but thinner, thanks to Corning’s stronger Gorilla Glass 2 and the further reduction of internal components. Our source suggests that the 30-pin Dock Connector is likely on the way out in the near future, and that a larger screen remains in the cards.
But I guess there will be much improvements on the iPhone 5 rear shells since Apple has been heavily experimenting with glass for years now. The next iPhone will have a larger screen for sure, but we don’t know how large it is.
No idea if we’ll see any clue about iPhone 5 on the iPad 3 launch tomorrow, just stay tuned!