The excitement has just about died down after the launch of the iPad 2 from Apple, but we are already building up a head of steam for the next big launch, the iPhone 5.Speculation is already growing too, with MacRumors citing Japanese site Macotakara for a new design for Apple's smartphone. As you can see from the mock-up image on this page, the glass backing of the iPhone is said to have been ditched, replaced with an aluminium rear. The reason? Well, according to Macotakara, it's down to problems with scratching, the weight of the galss and that old chestnut, the white paint job, which is threatening to finally hit the shelves over nine months after it was launched. The shift from glass to aluminium doesn't look as stylish, but it seems to be a lot more practical for everyday use.The other big problem with the current iPhone is the antenna. The same report claims Apple will also be abandoning the current external iPhone 4 antenna design, instead opting to add it to the Apple logo on the rear of the new handset. A clever solution. Let's just hope it is tested into the ground this time, avoiding more signal loss controversy.Interestingly, Apple was already rumoured to be making a lower-priced iPhone 5. Could the aluminium-backed iPhone be part of that plan rather than the new, high-end model? Only time will tell. Not a lot of time either, with the new model (or models) expected to be unveiled around June, which is a matter of weeks away.