Photo Reveals Apple iPhone 5 Likely to Receive A6 Processor Upgrade
Sonny Dickson, a 9to5Mac researcher and hacker, posted a photo to Twitter showing the iPhone 5's logic board containing an A6 chip.

Image Source: Sonny Dickson
"Yes, new iPhone will be an A6," Dickson succinctly stated.
Details of the A6 are still unknown at this time, but the smart money is on it being a quad-core processor, perhaps a derivative of Samsung's Exynos 4. The current iPhone 4S features a dual-core A5 chip, while the third generation iPad features an A5X processor with faster graphics.