the screen idea was cool, i know your minds instantly think wii u, but a centralized 3" screen could really be useful for inventory management in games. It would finally allow for better rts gameplay if designed right. Different devs would invent ways to have custom control layouts through a small touchscreen. the overall dimensions of the controller would only be slightly wider than it is now.
you could eliminate start, select, and the live button (or whatever its called) to allow space for the screen.
a front facing camera on the controller for face-time like video conferencing via skype.

not only are these cool ideas, i expect them to be present in the next box controller.

Ohh and a small speaker in the controller as well for conferencing. This makes more sense as the tv speakers could have the option to only play the sound from the game and the controller would project the audio from voice/video chat.

Honestly now that the d-pad has been fixed with the newer controllers I don't really want to see anything changed. Its my favorite controller for any system ever so just leave it as is!

I think adding a trackball or number pad would just make the controller even harder to learn for newer users and thus would be a mistake.

well I think it is time to have microsoft do some variation on the accessory hardware.... like having a basic pad for casual.... but having hradcore gamer pads also.... with some of the spec you gave.... i don't really like track balls as thumb stick as I think they'lll actually be less accurate unless you are very precise with your thumb or for very specific games.... try play a race game or sport game with that I doubt most people will be able to use it more efficiently than sticks..... but then again I don't see why you couldn't have the choice... especially since they make tons of money out of accessories..... the camera in the pad is useless if kinect is bundle same goes for mic.... I mean ok maybe if you walk around the house but still I'd rather have a head set then than walk with the pad always oriented a certain manner to my face.....
d-pad has to change (haven't tryed the new one though) but not the PS one that one gives me blisters the edges are bad and it's too thick.... not meant for hardcore endless gaming with a havy handgrip lol.....
I think they should just slightl;y improve what they have with better components and maybe some new functionality....

Decrease the size of the battery pack, keep the improved dpad and it's about perfect for me. The only other improvement would be on the reliability front, swap out the thumbsticks to some that are more robust to help stop the wandering stick syndrome that old pads get.

I wouldn't mind a steady evolution in the complexity and accuracy of a controller. The old, standard controllers could still be used by those afraid of change.

In my opinion the XBox 360 controller is almost a perfect design except for the D-Pad. XBox 360 controller feels comfortable in the hand and is more heaver and bigger in size compared to its rivals.

Small tweaks: improve the D-Pad and keep the 360 controller unchanged for next generation.

Agreed. If they could add in a touch screen without messing with the controller much, then fine, but it's perfect as is. (assuming an improved d-pad)

Without repeating myself from old threads. The 360 sticks need to be made better, they are very cheap and very short, make them abit longer and increase their range by removing some of that plastic around the sides. If they must keep the concave form they need to add some form of grip to them like the rough surface of the PS3 sticks.

Maybe changeable track ball/stick, therefore you can choose what to have where for playing certain types of games, I can't see a track ball in an FPS being very good, but like all things it would only require you to get used to it.

The 360 sticks do have bumps in them and since they are concave and not convex like the PS3, they already offer superior grip. They do need to fix the reliability, though. After a few months of Halo Reach I have 2 controllers that have issues. One of the thumbsticks on either controller now has a deadzone and and causes in game turns in certain directions to go rather slowly.