I always want more dynamic range, a larger colorspace, lower noise, higher resolution, etc. As for feautures, I stick with writing about those that neither my current or pre-ordered camera has but which are in other cameras or at least seem practical.
1) A built in horizon/level. I love the one on the D3.
2) A GPS. It would make geotagging much easier.
3) Wifi. It's available with an overpriced grip, but I'm not. Buyging that.
4) 3G. Why can't I upload my pics via the cell phone network?
5) A stablizied sensor. I prefer lens stabilization when it is available, but I'd much rather have both.
6) HD LiveView over HDMI. The 5Dm2 may have this, but I don't think so. 640x480 isn't good enough for manually focusing while shooting HD.
7) A mirror lockup button.
8) A built in arca-swiss tripod bracket...preferably L shaped. If not that, at least design the camera so that a more streamlined L bracket can be made for it.
9) A clock that adjusts for daylight savings time (or better, just end DST). With a GPS, I want the clock to autoset to local time.
10) Eye control focus point selection. I had this 10 years ago on a film camera and it worked. Why not on a DSLR?
11) A built in intervelometer. Why must I use a remote cable when I want to shoot an automatic series of shots?