Assuming you only upgraded for the legroom, I would still stay in PC and keep checking the map and you might be able to move to a window or aisle.
In the future, as long as you book a main cabin fare, empty exit row seats open to anyone (not saver unless assigned by gate agent) on the day of departure.
Along with the extra legroom in PC, you also get to enjoy earlier boarding which means better access to overhead bin space as well as free alcohol.