Was it inevitable? Technically no as there were repeated proposals for a demilitarised and neutral United Germany during and after the war. However in reality once both sides had a presence within the country during occupation neither side felt it could trust the other not to somehow cheat on the potential elections or gain influence in the neutral Germany via their political proxies (eg. The German communist party if elected would almost certainly have been loyal or predisposed to the USSR). So in my opinion unless the dynamic of the Cold War was radically different or the Allies or USSR had somehow gained sole control of German territory there was little prospect of a unified Germany being maintained once the war ended