So the question is what are the prerequisites for an escalation.
1. FF was not very much liked - neither by FJ nor by the A-H population (and definitely NOT by teh Magyar elite) - so FJ was really relieved that now Karl - whom he actually liked - was heir to the throne. So you would have to change the relation between FJ and FF (they really really were very opposite personalities) for the better to have a "personal" reason to go to war.
2. IMHO 1911 was the key year when Franz Conrad came out victorious against Aerenthal. Its quite an irony that the "hawk" Conrad got his way when in 1912 the Balkans crisis broke out. Remember the situation. The Ottomans were fighting a loosing war against the Italians when 3 Balkans nations took the opportunity and attacked the Ottoman Empire. Conrad convinced the Emperor that A-H could not allow the Russian friendly Serbs and Bulgars to expand. So the Austrian intervention quickly ended the crisis. THis led to further cooling relations with Russia on the down side (but there was no way the Russians and Austrians would have cordial relations anyway).
But the intervention led to an Ottoman Austrian friendship (Britain secretly was also haoppy that the Ottoman Empire survived this crisis). The minor border adjustments benefitted the Greek and did not hurt the Ottomans too much. The Ottomans also got a quite good deal with Italy as Italy feared Austrian intervention (Conrad was for it) and made a quick peace.
Suddenly in 1912 A-H turned from a declining nation to an active player again.
So there was no need to throw down Serbia (again) - Austria had proved its point 1912. It could be lenient in its demands and as long as Serbia punished the assassin(s) - which it did - all was well.
in 1916 FJ died and Karl ascended the throne. Karl was much more acceptable to the Hungarians and had good relations with the West from the start (young handsome a clever wife - immaculate behaviour). in 1921 Austria-Hungary was more powerful and stable than the 100 year before. The Russian revolution of 1921 and the civil war of 1921-1924 also relieved Austria of any fear that russia coudl endager its position. That left Italy as only "problem".
In addition Karl could reason that the White/Germany DOW made the Great war not a defensive war, so no alliance was triggered. A-H and Britain could sit out this "great war" (and make a profit in selling to both sídes
)
BUt I digress.
I believe if Austria had let pass the opportunity to intervene in the Balkan crisis it would be forced to be hard on (a stronger) Serbia in 1914.