I think there could be an increased risk of conflict. I think that nations would be willing to take risks with drones that they would not do if there were human pilots. Incursions into other countries territories could become more frequent. The information you could get about an enemies air defences could be well worth the loss of a few drones.A very interesting question
I guess the answer will evolve over time.
Do unmanned "things" increase of decrease the propensity for conflict?
The Chinese may well not want to fire on ships testing their right of passage through the disputed areas in the South China Sea but they might not think twice about shooting down a drone.