Well, if the German general staff had their was, their would of been war by 1916. Can they be held back? That is the question. Germany wasn't going to have another election for a while and even after it it would take the SDP a long time before they were able to do anything much to check the power of generals and industrial magnates. And it's not like there were a shortage of diplomatic crisis waiting to happen: there was revanchist Bulgaria with large parts of territory run by irredentist guerillas, there was the Armenian Reform Package and its consequences in Asia. And each diplomatic crisis had a very high chance of starting a war. Each of the protagonists had an overinflated confidence in their own abilities. Each of the protagonists had a substantial war-party. Each lived in fear of being caught napping by the others. War plans were based on an assumption of first-strike which required rapid mobilisations based on tight schedules. As soon as war loomed, countries had to start mobilising to prevent being cuaght with their trousers down, but once they mobilised, others had to mobilise. You know have a bunch of mutually suspicious powers, all believing they'll win a war, and all with nationalistic fervor raised to fever pitch.
If you somehow navigate each crisis without everything blowing up (wierd and whacky domestic politics could stay hands, such as the frequent speculations about how a civil war in Ireland would have affected Britain's freedom to act in Europe, and if Franz Josef were to fall down some stairs, Austria would be in rather a bad way vis-a-vis Hungary), then after 1916 things subside. That date was when the Generalstab believed they had to go to war: after it they may be more cautious (then again, they are Prussian militarists...). Another factor is that Germany was clearly going to loose the naval arms race and would have to find some way of bowing out. Bulgaria's revolutionaries can fulminate all they lack, but nobody will get worked up about the snow melting on the Balkans unless its for self-interested reasons. So I'd imagine that in remarkable and unlikley circumstances, it might just be possible to avert WW1 altogether with a PoD concerning Fran Ferdinand.