Here are the results from a survey which I conducted on this site last week in conjunction with my article looking at body and lens based stabilization systems. These results are based on responses from about 400 Canon EOS users plus a few users of other camera brands. I'll list the questions of interest and the responses I received (percentages rounded off to the nearest whole number).
To give lens based IS a fair chance, the questions assumed that it was slightly more efficient then body based IS, though that may not always be true.
Q1 - Which would you prefer?
Q2 - How much extra would you be prepared to pay for a body that had IS built in?
Q3 - Would you switch brands to get boby based stabilization (e.g Move from Canon to Pentax)?
Q4 - Would you be interested in adding a body with built in stabilization you your current camera bag, even if it was just an entry level camera (e.g. Digital Rebel)?
Q5 - Even if the camera body offered image stabilization, would you be prepared to pay about 25% extra for a lens to have a stabilized viewfinder image and possibly slightly more effective stabilization?
Q6 - Do you still shoot enough film to need stabilization in the lens?
The overall conclusion here is that while users are happy with lens based stabilization, a significant fraction want at least the option of body based stabilization and would be prepared to spend an additional $100 to get it. This conclusion is based on four results:
The factor that's probably making Canon hesitant to offer body based is the possibility of declining sales of IS lenses, however 67% of users would be prepared to pay and extra 25% for IS in a lens if it offered slightly better performance and a stabilized viewfinder image, so offering a body with IS wouldn't be the death of IS lenses.
The vast majority of users (92%) don't care about image stabilization with 35mm film cameras (which would require lens based stabilization)
I suspect, given these numbers and given that pretty much every new DSLR from Pentax and Sony (and now Olympus too) has body-based stabilization, including the new Sony 24MP full frame DSLR to be released later this year, Canon must be seriously considering adding body-based stabilization. You can see why they are somewhat reluctant to do so, they have a lot of time, money and reputation vested in lens based stabilization. However users don't really care about that. I suspect users want stabilization with their existing lenses which aren't stabilized. Additionally many lenses (especially wide and normal primes) and are not even offered in IS versions, and for various technical reasons probably won't be. A stabilized 85/1.8, 50/1.4, 50/1.8, 30/2 or 24/2.8 don't look very likely and even if they were introduced, who wants to sell existing lenses and pay more for new ones?
Could Canon offer both stabilized lenses and a stabilized body and could the two work together? The answer is certainly yes, though probably only one stabilization system could be operative at any one time. In fact such a dual system does exist - The Olympus E-510 has stabilization built into the body, and there is one stabilized lens (the Leica D Vario-Elmar 14-150mm/F3.5-5.6 ASPH/MEGA O.I.S.) available which will fit on the camera! Olympus aren't intending to make a dual stabilized system themselves, since they have said that they think the future lies in body based stabilization.
So based on this survey (and my own feelings on the matter) my word to Canon would be this:
"Give us an image stabilized body so that we can get the benefits of stabilization with our existing non-stabilized lenses. We also want stabilization with normal and wideangle primes, which you are unlikely to give us for technical reasons, and even if you ever did, we don't want to have to buy a new set of primes. We'd even be happy if you just put body based IS in a Rebel class body and charged us an extra $100 for it. We don't care is body based stabilization is slightly less effective. When we need lens based stabilization, we'll still buy IS lenses"
The longer Canon keep us waiting the closer I look at the Pentax K10D, the K20D, the K100D and the K200D line of cameras. I don't think I'd "jump ship" totally since I have an investment in the Canon EOS system and lenses and I'm very happy with their performance, but I certainly might add a image stabilized Pentax body and a few prime lenses to my EOS outfit if Canon don't give me the option of buying what I want from them.