If there's no 1914 crisis - the entire premise behind everything I've said so far - then the Austrians won't have the proper casus belli for attacking Serbia. Franz Ferdinand will ascend to the throne and Slavania will be created out of Bosnia and formerly Hungarian territories, creating a Triple Monarchy. Serbia will probably continue making trouble after that, but with equality within the Empire, the South Slavs under Vienna's control will be much less likely to go over to their side. Eventually, the Serbs will either stop their dissent fomentation or they'll get caught, both of which end in a rapprochement with Vienna as they had before the murder of Aleksandar.
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Why would the South Slavs unite behind a Serbian-dominated banner if they can stay in the Austro-Hungarian-Slavanian Triple Monarchy and have peace and prosperity instead, with equal rights thrown in for good measure? Serbia sure wasn't going to give those up to their fellow South Slavs (we already saw that post-1913 with the Macedonian situation and in OTL after 1918 in Montenegro, Croatia, and Bosnia). Besides, by the time 1914 rolled around, a lot of Serbs were pissed off enough with Dragutin Dimitrijevic to start to abandon his policy of fomenting rebellion in the Balkans; this process will speed up if Slavania is created. I don't see Serbia having the ability to effectively foment rebellion after that, nor do I see them particularly wanting to.
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All in all, I don't think that Serbia has the ability to successfully lead a Balkanian revolt after 1914 if the Entente Powers have nothing to do with it. After 1916 and Franz Ferdinand's succession, they don't have the ability even if the Entente assists them due to the existence of Slavania. It's not just the overwhelming military force that the Entente Powers have, but the ability to appeal to stability and equality with the Germans and Magyars, which is more than Serbia can offer. There is simply no incentive for a general South Slav rising.
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Britain also lacked the money with which to resist the coalition, money that Austria-Hungary-Slavania would have, if not from their own coffers then from the Germans, who certainly aren't interested in a South Slav revolt. Comparing the two is apples and oranges. Yes, anyone would concede that there is inherent possibility for a miracle to happen. But circumstances and the massive power that a Great Power and a major regional one can bring to bear militate against even a minor likelihood that a South Slav uprising will succeed.