Including or not integration between IM and SMS, this will be the second Apple stab to traditional telco operators revenue - Facetime was #1 - since iOS will exchange free messages among iOS users, perhaps even OSX users at some point (same route as Facetime), going around SMS. Of course, IM is nothing new, just like video calling was nothing new, but what is relevant here, is that #1 mobile platform (according to yesterday's keynote) is replacing/extending the standard mobile device messaging system, SMS, with IM, and that opens doors for a much clever system, and where the traditional telco operator is not involved, other than be the data pipe if 3G is used instead of Wi-Fi.
The details about iMessage system are almost none, besides what you can view at the keynote video (iMessage is announced at around 1h and 11min), the Apple SVP just slips the detail that it will use the proven and reliable Apple Push Notification System, which serves billions of notifications. If I remember correctly this system uses XMPP. In humble opinion Apple is in the right direction, choosing finest standards for each functionality needed, SIP for call control, XMPP for IM.
In my mind there are a few doubts for what is coming next, the first about iOS 6, will there be an iVoice/iCall, closing the circle and providing a final stab into operators? The second, related with Android, will Google turn GTalk the main messaging system too, with SMS integration, and put SMS as "past" feature for old mobile phones? The third related with all mobile OSes, will there be any interop?
