ThinkSecret has compiled their summary of what they believe that MacWorld SF will bring.
Most significantly, they echo CNet's report that Apple will start charging upgrade fees for certain iApps. They also report on an introduction of 802.11g -- a new an improved Airport protocol. Finally, they stick to their previous report that no new hardware will be introduced.
The possibility of an iChat update and an Apple branded browser remain on the list, however.
Addendum: ThinkSecret also mentions that a Mac Tablet wouldn't be a complete surprise.