(rumored) 100-300 f4
I know its just a rumor, grain of salt and all that, but if true, this is the lens I, and i assume many others, have been waiting for.
IMO, a prefect match for the 24-120 f4.
For people who need the range and above-average image quality but arent pro sports/events shooters, where the speed (and associated weight, size, and cost) of a 2.8 isnt needed.
I hope this one is true!