Fir of all, if it is a Q3 release, my vacation at the end of Q2 beginning of Q3 will have to live with the 7D and 50D I currently own, and that sucks.
Secondly, if it is a Q2 announce and Q3 release, prototypes are not a word used at this point. There might be some firmware changes between cameras. But these would be Beta or pre-production cameras.
As far as problems writing to the CF cards, those issues should be long found in regression tests and such. I would hope. I would expect bugs will be a minimum, there will be some. But I would also expect any photographer to have a few 1000, or more exposures on any new camera before they head to the sporting event, no?
Like seriously, who would grab a new camera and the start taking event pictures, unless you absolutely had to??
I have been in production development for a while now, and unless Canon is an absolute broken mess of a large corporation, I would expect there is significantly less risk with than some of y'all think. I have to expect these cameras have already been vibe-table tested with accelerated aging tests, temp testing for both environmental use, but again accelerated aging tests, regressions tests, life tests and so on.