Canon already announced 4 cameras recently (40D, 1D & 1Ds Mark III, 450D) so my guess is that they updated the cameras which can already has a huge market base. I think 5D sales isn't doing so well because they slashed the price a number of times already. From a marketing POV, the 5D is stuck in a rut right now. Why? If it was good, they would have released an update already. Even if they release an update, it would be tough to market since the competition is going to get rough. You can't have all the bells and whistles because they don't want to cannibalise into the 1-series line-up or too little features which is going to make it look an expensive 40D DSLR with fullframe sensor.
So you guys can wait long long before they come up with a 'decent' update to the 5D. I mean who knows they might release a power packed kick ass DSLR but I highly doubt so. One thing for sure, the Print Button will definitely stay. LOL!! We can only continue to speculate. Cheers!