
The patent I mentioned above was published back in March, and describes an interface similar to that currently used for the SMS interface of the iPhone, but with a bunch of key changes, including a list of suggested keywords, and since the drawings included with this patent points to "Instant Messages" in a lot of places,everything looks obvious to me.
Just check the abstract: "A portable electronic device for instant messaging is disclosed. One aspect of the invention involves a graphical user interface (GUI) on a portable electronic device with a touch screen display. The GUI has a set of messages exchanged between a user of the device and another person. The set of messages are displayed in a chronological order. In response to detecting a scrolling gesture comprising a substantially vertical movement of a user contact with the touch screen display, the display of messages are scrolled in accordance with a direction of the scrolling gesture. The detecting of the scrolling gesture is substantially independent of a horizontal position of the user contact with the touch screen display."
Considering the above, I think there's no doubt - the iPhone will finally get instant messaging features, but we have no idea yet about the time when we'll see it happening. Anyway, I am sure Santa won't catch us without instant messaging on our iPhones, but this may even happen as soon as June, together with the release of the 3G iPhone.