If you killed Hitler, then the generals who HATED the way Hitler micromanaged the war would have been able to run things their way, and maybe WWII would have been WON by the Germans.
Himmler had the Waffen SS and the entire SS at his disposal to oppose the Wehrmacht. And I believe Hitler loyalists in the ranks would have revolt.
The Nazi Party was full of personal rivalries and animosities, Hitler was the glue that kept it all together, no one else would have been capable of uniting all of the various factions.