According to AppleInsider, these updates wouldn't be major and would basically constitute a streamlining of the entire line. Since the internal makeup of Apple iMacs and notebooks is similar, we might see an NVIDIA chipset update.
An added mini-display port is also a likely addition. Whether or not firewire will remain or be removed is uncertain at this time. Of course, this is just a rumor right now. We'll have to wait and see if this turns into anything. One thing is for certain, though. A big event is unlikely. If updates are imminent, Apple will likely roll out the updated versions without much fanfare.