What if Franz survived the assassination attempt by Princip due to chance? Potiorek, the military governor of Bosnia was riding with the heir to the throne on the running board of the car, but happened to be on the opposite side of the Serbian assassin. What if he were on the other side of the car, and when Princip fired his shots, Potiorek's body shielded Franz from the bullets? The royal couple would be showered in blood, but still alive as the assassin runs off.
What does that mean for Serbian-Habsburg relations? Franz was probably the best thing for the empire's survival and a somewhat competent military man that was known to reign in some of the worst habits of Conrad von Hötzendorff, head of the K.u.K. army. What does his survival mean for the empire and how does the assassination attempt affect him?