No 1914 assassination certainly doesn't solve the Balkans and Slav grievances.
Looking for all possible ways conflict could still arise:
Hungarians balk at USGA plan and rebel, possibly looking to the Balkans for allies (willing to give up Croatia for support for example)
Germany launches pre-emptive strike on Russia. This will still lead to a two-front war unless by the time they attack they decide against the Schiefflen Plan and the French government falls into coma, no way France is letting Russia fall, however such a situation might see the intial focus put on the Russians.
The CUP nationalist government in Constantinople panics over the Western plan to create a 'free' Armenia (plans for this began in early 1914), and goes on the war path. Unless the Pashas have a death wish this might fit into a German pre-emptive attack on Russia.
Germans continue encroachment into British oil monopoly in Iraq via the Berlin-Baghdad Railway, causing the British to launch their own pre-emptive strike, or at least cook up a crisis to seize the region (this was a nice practical advantage to aiding plucky little Belgium in 1914 as well, the first British troops deployed were in Basrah after all)
Another Moroccan Crisis or something similar, maybe. After the 2nd Crisis I think even the Kaiser got the gist that the Entente was pretty united.