If we don't count the severe internal problems of the Empire, in plain military terms, the situation was not much better:
1. Despite the Brest-Litofsk treaty, the critical situation in the East does not leave a safe environment, while no inflow of rare sources nor industrial nad agricultural products were obtained.
2. In the Western Front the Allies had already proved they could take the initiative, while fielding more forces and advanced equipment.
3. The fall of the Balkan Front created a situation in which the status of the A-H Empire was in peril, no matter how many troops the Germans could sent.
So, yes I'd agree that late Spring or June 1919 is the limit.
Hence, there could be two concequences:
1. The Entente faces huge internal oposition during late Autum 1918, and accepts a ceasefire with better terms for Germany: less land for the Polish, no Rur-Saar production commitment, less compensations, perharps the survival of the A-H monarchy, but still Czechoslovakia emerges and lands to Romania, Poland and Yugoslavia.
2. The Entente maintains its offensive and worst terms of peace: perharps division of the German Empire as well...