Developer John Heaton recently discovered hidden code within iOS 5 pointing towards iChat services. These include Jabber and AIM, services which are currently not supported on iOS.
Of course this led to speculations that Apple might include iChat in iOS sometime in the future. There’s also a possibility, as reported by MacRumors, that Apple is planning on introducing a general IM framework with support for Apple’s IM protocols, even if actual services might not be supported or available on certain platforms. iChat on Macs includes support for services like AIM and Jabber but iMessage is currently not available, even if the offering is already being rumored.