If I had to pick what I would like to see in the next 7D, it would be something along the lines of the following:
7D Mark II
- 18mp APS-C (possibly 16mp, if necessary, to achieve below)
- Improved QE from 7D I (which is about 41%) to at least 50%
- Same low read noise as 5D III
- Improved high ISO by a stop (ISO 12800)
- This may be asking for too much...I'd be happy with lower-noise ISO 6400 and 3200!
- Increased frame rate to 10fps
- (I'd like 14, but even that is relegated to mirror-lockup mode in the 1D X...I'd be plenty happy with 10fps, and if thats not possible, 8fps is still great!)
- Increased continuous frames, to at least 25 (up from 15 in original 7D)
- Improved AF system, such as a 41pt all cross-type reticular AF with similar APS-C frame spread, point expansion, zones, etc.
- Maybe get that nice center vertical strip of doubly sensitive cross-type points the 1D X has
- Dual CF (or CF/SD card slots, although dual CF is preferable), and/or support for faster cards to support a longer continuous buffer (35 frames maybe...would be REALLY nice?)
I'd be PERFECTLY happy with the next 7D remaining as an 18mp sensor. If Canon can reduce read noise to acceptable levels, 18mp is a great resolution (and based on some of my poking around with the sample 5D III shots available from Canon in Photoshop and Lightroom by tweaking levels or exposure...I have yet to see a scrap if high or low ISO fixed-pattern banding noise...so I think the read noise problem has been taken care of with Digic5+ and however Canon is fabricating sensors now.) I'd even be willing to drop down to 16mp if it helped lower photon noise a bit more, which would make ISO 3200 and 6400 more usable.
One of the things I run into a lot with my 7D is that memory card space fills up FAST. At 8fps on a 16Gb card, you get about 600 RAW shots. When your firing away in burst mode, you can drop 20+ frames in a few seconds. It would be nice to have dual slots and the ability to automatically switch to the secondary when the first fills up. For those situations where your in extreme environments...pouring rain, muddy swamps, raging blizzards...it would be nice to allocate the second card as a backup, in case the first gets damaged.