I guess when the D200 came out with its professional quality body, weather sealing etc., Canon was caught on the wrong foot.
Nikon also probably had a few versions on the table and after Canon announced their final version, they quickly put their D200 "weather-sealed" version with built-in flash at an attractive pricepoint, and then made final adjustments to the manufacturing line, accordingly.
I have heard a rumor that the reason for the 200D, it's weather sealing and it's price point is becuse Nikon have lost the professional market to Canon, and that the 200D can have the weather sealing and functions without having an impact on the sales of the expensive professional cameras from Nikon as that is a loosing market for Nikon anyway. I have no idea if this is true.
The 200D is a tuff competion in the amateur segment, and maybe even in the proffesional segment since the price is so low.
Is there anybody that know the salesnumbers of the different model from Canon an Nikon?
So based on the above, the only way Canon can grab the spotlight back, would be to put a 35mm sized sensor in the 20D replacement, with around 10.4MP resolution and the pixel pitch of the 5D and the built-in flash but without weather-sealing etc. Leave the cropped-sensors to the "Digital Rebel" arena. At a pricepoint of around $1900-2100, it would sell very well. But that will cannibalize sales from the 5D, I would suppose.
Just a conjecture...
I think you are rigth, if Canon makes a camera with weather sealing they will canibalise there profressional (1D) sales.