iOS 5.1 beta hints at quad-cores for next-gen iPhone and iPad
It is believed that the core references Apple uses begins with the number 0 and therefore the single-core processors found in previous iOS devices were referred to as /cores/core.0. The dual-core A5 processors that are currently being used inside of the iPhone 4S and the iPad 2 are referenced with the code /cores/core.1. The code in question here is /cores/core.3 which would be used to reference a quad-core processor when following the pattern. As you can see they skipped the reference code /cores/core.2 which would have more than likely been a triple-core processor.
source: 9 to 5 Mac