What is going to happen?
This is my take
1) No invasion of Serbia. No ww1.
wikipedia: "He also advocated a careful approach towards Serbia - repeatedly locking horns with Franz Conrad von Hötzendorf, Vienna's hard-line Chief of the General Staff, warning that harsh treatment of Serbia would bring Austria-Hungary into open conflict with Russia, to the ruin of both Empires."
2) the previous Dualism in the Habsburg empire of Austria and Hungaria is turned to a Trialism Austria-Hungary-Southern Slavia and the empire is granted further decades of survival
3) possible clashes with the Hungarians which will see their privileges curtailed under his rule
What do you think about the topic?