Well, there's always that perennial aspect of the Third Republic, namely domestic instability that could lead Hitler to do something really ballsy like re-occupy the Rhineland, but OTOH that would require at least averting a crisis with Mussolini. Or the Italians could do something to intervene in the British sphere of influence and that whole Stresa Front thing collapse.
If there's one thing that can put an end to domestic instability in the Third Republic, it's a resurgent Germany. We've seen it in 1938, and again in 1953--every time the Germans look like they're getting up, all the French politicians except the Communists make sure to preach national unity in the face of unnamed threats.