It seems to me that (nearly) everyone assumes that had war not broken out in late July/early August 1914, given the regicides (to use the term loosely) in Sarajevo, it was merely a postponement; that is, sooner or later it was inevitable given the state of interlocking alliances and arms races. I'm asking this: who says that particular state of affairs continues forward much beyond 1914?
Consider: Charles, Franz Josef's successor in Vienna, was a far more modern and compassionate type than his predecessor. While there doesn't seem to be a great deal of documented evidence one way or the other, I suggest that his application of his faith (in OTL) would have led him to liberalize the Habsburg dominions significantly in an alternate timeline in which war didn't occur after the regicides in Sarajevo. A liberalization would probably have done much to defuse tensions in the Balkans, especially if the south Slavs were granted significant measures of autonomy. I realize that might get the Hungarian nobles rather incensed but a liberalization that benefitted the average types might well also squelch any attempts at counterrevolution through sheer numbers.
Consider: Nicholas II had his son with him at Stavka through much of the conflict, where he was under more-or-less constant supervision and protection. In the absence of a conflict, that doesn't happen and he's able to roam the various palace rooms and grounds largely freely. An otherwise-unremarkable household accident could quickly turn fatal (e.g., a seemingly innocuous head bump leads to a massive, rapidly increasing hematoma, resulting in death). If the Tsarevitch dies, Rasputin is discredited, as is the incumbent branch of the Romanovs. Kerensky and friends/allies would likely force the issue of Nicholas' abdication in favor of perhaps his brother Michael or his uncle the Grand Duke Nicholas. Now, you have a sea change in St. Petersburg, wherein focus on internal reforms rather than an arms race becomes primary.
Consider: residents of the Reich look across the border in 1916 and thereafter, seeing the increasing freedoms in Austria-Hungary and ask, quite naturally, "why not us?" That sentiment sweeps the German Empire until it's evident to even the most rigid reactionary that it's a case of give in or go home, as it were: the alternative to liberalization would be a sweeping revolution. Now you have the stage set (after some epic royal histrionics, of course) for a far more liberal Germany--focused, like (oh, the irony!) Russia on internal reforms rather than an arms race.
OK, these are just rough ideas, but I suggest that a sort of inverse domino effect might just head off European conflicts for a generation or so--say, until the 1930s or thereafter. Have at it.