As Apple gears up for the release of the next generation of iPhones, more and more customers are rushing to trade in their old handsets.

Apple has not even confirmed the iPhone 5's existence, let alone next month's launch, but U.S. former Vice President and Apple board member Al Gore has said new iPhones will be unveiled next month.

The tech trade-in site Gazelle reports an 85 percent rise in iPhone trade-ins. NextWorth, a tech buyback service, reports that prices on old iPhones are decreasing as people dumping their old handsets increase the supply as the expected release date draws near.

Sellers are trying to get the best value for their old iPhones while waiting for the release of the new one. But delays on the release may make their plans backfire. There were also some rumors on iPhone 5's delay, but that is yet to be confirmed by Apple.

Traders believe that the rumored iPhone 5 specs and features are worthy of the upgrade. According to rumors, the iPhone 5 will have a faster processor, larger screen and 8-megapixel camera.

Analysts speculate that Apple will unveil two devices: an improved iPhone 4 called iPhone 4S and a new iPhone with completely new design and features, the iPhone 5.