iPhone 5 could incorporate a Thunderbolt port, but this might not be such good news, as it could mean users paying more and becoming even more locked in to Apple's ecosystem.
Thunderbolt is based on the (Light) Peak technology created by Intel. The advantage is that data can be transferred and synchronized faster than using USB 3.0. The downside is that it is power consuming. Since users usually connect their iDevice to a power source when they transfer data, they may not even notice this downside.
The transfer speed may be the only advantage thunderbolt has over USB 3.0. USB 3.0 slots use less power, have a higher compatibility degree, are less expensive to manufacture and, unlike Thunderbolt, they are backwards compatible. Thunderbolt limits supplier choice, is expensive and is compatible with only 0.1% of the devices available.
All in all, Apple has made a strange choice which aims at locking users in.
Thunderbolt chips are provided by a sole supplier, Intel, and Apple at present has exclusivity. Thus Apple and Intel can fight off competition and hike up prices for iDevices. Intel can ask for more money for their chips thus making non-Apple devices cost more. This could be seen as monopoly practice.
Users are the ones who have to pay for such practices. Because of Thunderbolt they may have to pay more money for their iPhone 5.