Canon have a large enough range that theres always going to be one camera or another about to be updated. I take the view that if the camera does what I need, then why worry about more bells and whistles.
I still use a 30D, which will do me until the 1Ds mk4 appears. It was my introduction to digital and was bought only about 3 months before the 40D appeared, but that did not bother me at all. I have seen newer bodies come and go but made the concious decision not to upgrade until I can get at least 4 times the 30D's 8 (and a bit) MP. If the 1Ds4 is anything like its rumoured to be, I expect to still be using it in 10 years time.
So you see my mindset. Based on that, my advise would be to be very honest with yourself about what you need a camera to do. As others have said, video is the newest gimmick, but do you want it? Do you want to print at A2 or bigger, or will A4 do? Do you expect to shoot available light images in a coal hole or at midnight or could you cope with less than stratospheric ISO's? Answer these questions and many others and you might find that you are focussing in on an existing camera rather than hoping that an as yet unannounced one will be the answer to your prayers. On the other hand should you decide that your analysis has shown you that you do need the 5D3 or 8D (or indeed like me the 1Ds4), then so be it.