I use it for wildlife photography (birds) and here is my wish list:
Usable ISO of 12600 (2 stops better), a lot of birds in primary forest require high iso.
A speaker jack would be sweet; I record the bird call (using Rode Videomic) and then playback to call the bird. If I could connect it to external speaker to boost the audio would make it a supper usable tool. Some bird guides use a separate equipment for recording and playback that cost a bunch. Having this recording and playback capability in the camera is very-very useful. Most birders that have a camera use a 7D with 100-400 mm.
Increased zoom in playback mode for pictures is also very usable. I use this camera to help me confirm bird ID so when I zoom-in, I would like to get a bit closer in some situations.
In camera edit (shadows and highlight adjustment) is also very desirable. In many cases it is required to raise the shadows and lower the highlights to get better confirmation of bird ID. Many times I am better able to ID the bird when I edit the photo with Photoshop, so it would be nice if I could adjust the images in the field for a better, quicker and positive ID.
Of course better definition would be supper welcome, again this would help in the bird ID process.
Keep 1.6x, it helps a lot to get 1.6x on the telephoto without having to carry a lot of weight of big lenses.
Better weather sealing.
Increase the camera-presets (c1,c2 and c3) storage from three to four or five and keep the wheel selection. I pre-program the optimum photographic settings in theses presets and the wheel makes this selection almost instantaneous. For example my bird in flight (BIF) settings include AI Servo, Multiple Point AF, +3 Exposure compensation, 1/2000 sec speed and of course Auto ISO, and speed priority. When I see a BIF I instantly shift my camera to optimum settings (c3) and shoot the bird without any delays. It works great!! Please dont change it to some thumbwheel setting that I would have to look. The current wheel can be set to any of the three settings without any delay, and I always know where c3 is because the wheel does not turn any further. When required I can confirm the position of the wheel by turning it to c3 and then counting back to c1 or c2 without even looking at my camera and very quickly.
The switch from video-to-still is too stiff, when it gets slippery (from my hands oil) it is difficult to switch, so make the little handle bigger for more torque with less force.
Video auto focus would be very nice. I find myself focusing in still mode and then switching to video mode for crisp video. When I use LiveView mode many times I do not focus properly and do not realize until I am home watching the video. Too late, scrap that video and that is really bad because video is very important for me. The LCD cannot be used for proper video focusing due to reflecting light and size, maybe if the zoom button worked in video for focusing purposes would be great ie. 5x and 10x zoom for stills works great.
That is it. Otherwise I love my camera and hope that someday the 7D II will have all this great stuff that will make every birder buy this as a must-have tool for improving bird ID accuracy.
Here is a blog I wrote explaining some of the benefits of photography in birding:http://10000birds.com/photography-and-birding.htm