Good title . I hope we do eventually see a D400, seems like Nikon has bitten off a pretty big production chunk right now and with the D800 flap smooth sailing might take another detour.
I keep a small amount of black gaffer's tape on each of my lens hoods (store it there) and a larger amount run down the leg of my tripod for in-the-field emergency use. Sometimes I use it for a cable tie, or to keep a auto-focus lens manually focused, and maybe just to keep a rubber door shut so I don't have to worry about it.
JFFT (just food for thought).
FWIW, the door design on my D700 seems to be holding up pretty well, the D200 was another story and perhaps the same as your D300. Maybe there is progress .
Roger It's still, ISO, aperture and shutter-speed, right?