Volaris Costa Rica inaugurated service to IAD last month and Virginia's governor and DC's mayor attended along with airport officials:
https://airlinegeeks.com/2018/05/17/...er-for-dulles/
Timing for the Volaris flight is even later than the CX flight, with a 11:35 p.m. arrival into IAD and a 1:52 a.m. departure.
Based on that I think chances are pretty good something similar will take place for CX especially since CX serving IAD is of much higher significance.