The few things I would like improved for the next 5D installment are pretty much the same as everyone else.
1. 7d Autofucus or better
2. Better ISO (D3s or better)
3. Pop up flash for wireless flash control and also for the occasional time when you don't want to carry a flashgun e.g Family holidays etc
4. 60p video
5. Don't really want more resolution, but if they introduced pixel binning that was a benefit to the ISO, that would be cool.
6. Also want Canon to use same grip as the Mark 2 or at least allow it to still fit.
7. Would like a Crop funtion 1.3 & 1.6 for creative in camera croping. Also a funtion that allowed you to crop a photo in the camera after it has been taken. But I wouldnt be anoyed if they didn't do this as its not a big deal.
I know this is a bit of a repeat of what has been said but felt I had to add my list, just in case Canon is watching as this topic is getting a big response. I hope they are as there has been some great ideas and suggestions on this topic.