Even if the Archduke escaped the assassination attempt, we were headed for war by latest 1916 because all the major powers in Europe were furiously arming up to protect their colonial interests and all it took was another spark to trigger off the war. Remember, the Alsace-Lorraine region of France was a disputed area that the Germans wanted, and that dispute was enough to get France and Germany into a shooting war sooner or later.
Actually, in 1914 Alsace-Lorraine was part of the German Empire, the Germans having taken it away from France in the 1870 war.
IOW, it was a German region the French wanted back.
They got it back after WWI, lost it from 1940 to 45, and have kept it since.
The area had alternated from German (to the extent that term had any meaning) to French control in previous centuries too.