However, if recent history is of any value, I think that Canon will do an incremental upgrade - i.e. solving the problems of the current version more than reinventing it. There's a 400/5.6 prime too, and they probably wouldn't cannibalize it.
So sharpness-wise I don't think the new model is going to be a lot better. I think they will keep the best selling points being new IS and smoother bokeh. Maybe weather sealing? The push-pull design is a specific feature of this lens and they might well want to keep it.
Hey, thanks for my morning laugh – it was a good one!! How could a brand-new lens with the latest image stabilization system and the same focal length and max aperture NOT cannibalize sales of a 20 year old lens?? The only possible answer is by the 20-year-old lens being substantially cheaper, and no matter what, the old prime is going to be substantially cheaper. Besides, there are four 70-200 zooms and a 70-300 zoom in the L-series, along with the 100-400, and you think Canon is worried about cannibalization? For most people, a telezoom is the second Glenn's purchased after a standard zoom - Canon is very wisely offering a great selection for that choice.
As for sharpness, don't worry, the new lens will be significantly sharper than the one it replaces. Think 70-200/2.8 IS differential. I suspect the only people who believe there won't be a substantial boost in sharpness are Nikon fanboys (in or out the closet) who want Nikon to finally have an xx-400mm zoom with IQ that rivals Canon, which they do...and will continue to for however long it takes Canon to get the new 100-400 to market.
Great, I'm glad that I made your day. However...
- I don't see cannibalization between the 70-200 as they are differentiated in price, aperture, and IS. They go by the simple principle that you pay more for wider aperture and IS and they serve different segments of the market.
- The 70-300L and non-L are differentiated very well in price and performance.
- The 70-300L and 100-400L are differentiated by those 100mm of focal length and portability.
- The 400/5.6 has been for many a 1:1 alternative to the zoom. Similar price, similar application, better IQ at the price of less flexibility. If the new 100-400 puts it to shame, the price will reflect it and so again no cannibalization. If they can make a much better zoom, they can make an even better prime. Eventually Canon will release a new 400/5.6 and the situation will be even again.
In my previous post I clearly stated that the price of the new Nikon 80-400G is ridiculous, but Nikon can get away with that because the previous version was crappy and the upgrade is substantial. The current 100-400L is quite good and making it astonishingly better will be more difficult. If they do, the price will be such that many will wonder if the previous version was a better deal. So I don't know of what imaginary fanboyism you're talking about.