Good point, Lionheart.

The faster lenses are generally the professional grade equipment which, in turn, have better glass in them. In Canon's line, these would correspond to the "L" lenses. So if Canon started to produce new L-lenses which are slower (to keep prices low) but had the same glass in them, you would save your money by buying the slower lenses?

I think Canon may have already started this trend with their 24-105mm f/4L IS. At the time, I went with the 24-70 f/2.8L instead because of that 1 stop increase and I didn't need the IS feature in this range. The cost was near identical between the two and I am very curious which becomes the better seller in about a year.