IMHO the Munich Accord was the point of no return. The Rhineland, Anschluß, re-armament all enhanced Hitler's prestige internally. Failure at any of those points might well have resulted in reversal of the Nazi dictatorship or keeping it caged in Germany. With Munich, and the subsequent dismemberment of Czechoslovakia, it became apparent that the anti-German alliance system was a sham. Furthermore Hitler now had five years of "proof" that his plans for continuing expansion and war were viable against a soft and squishy west. The success of Munich and the subsequent Czech dismemberment also convinced Stalin to switch horses which led to the Molotov-Ribbentrop Agreement. Had the UK and France supported the Czechs, even with some nods to a more privileged minority status for the Sudentendeutsch but no border changes, the cascade that led to September, 1939 is halted. After that, hwo knows - would Britain have tolerated Plan z, and so forth.
Of course the usual "Hitler dies in a car crash in 1931" sort of thing could very well prevent WWII, were any other Nazi leaders charismatic and driven enough to achieve the electoral success and push themselves in to being Chancellor (and then go to rule by decree)? My point is that here I agree with Churchill to a large extent, had the British and French stood up to Hitler between 1933 and 1938 at some point, and done so quite firmly, WWII in September, 1939 would not have happened. Would Hitler have been thrown out? Would the Nazis have been replaced by something else? Would the generals have "pulled the trigger"? Hard to say.
Absent war starting when it did, with the resources of an intact Czechoslovakia under German control, could Germany have sustained the rearmament plans? This is doubtful, and the consensus seems to be that British and French rearmament/reorganization was going to leap past Germany in the near future. Also, of course, an free Czechoslovakia as part of an anti-German coalition would make life miserable for the German military...