Personally, I would like a trackball/pad even on touchscreen devices, there's plenty of times when you could use your device quicker than with the touchscreen e.g. reading a bunch of emails you wouldn't need to get in the way of your reading just to get the next email you wanted to read and when there's times when it wouldn't be better to use it you wouldn't have to, so where's the loss in having one other than losing a little bit of space from some buttons that are large enough anyway.