iFixit has taken extensive looks at the iPhone 5 and its lightning connector. Right now, the iPhone 5 only supports speeds of USB 2.0. There is no way around that. However, they found something interesting about the connector.
The connector has some extra pins and this would make it compatible with USB 3.0. Again, the iPhone 5 only works with speeds up to USB 2.0. However, it’s possible that a future device would work with this sort of speed. If anything, it’s Apple ensuring that their devices are future-proofed for a at least the next several years.