Given ORD will be a new port for CX, I won't count on it 100%. If you really in a hurry to get the bag after arriving HKG, I suggest on your PIT to ORD leg, have your bag tag to ORD only, pick them up from the carousel then re-check @ CX counter.

This a the most troublesome way of ensuring it.

Or you could ask for a extra spare tag when you check-in HKG-ORD. When checking in at PIT, you can then tag the priority tag to the bag by yourself.