I don't think Pace has the long term job security to take a QB early. If he did have that security and thought he could get a starting QB somehow its not beyond belief that he'd pull that trigger.
Trubisky has one year left and Foles has an out for his contract in 2021.
I just don't see that Pace has that long term security - his signing of Jimmy Graham appears to be a short term desparate move. At least for now.