There were several attempts to kill Hitler, most famously probably the 20 July plot.
So… what would have happened, if that e.g. succeeded?
Now, as I do not want to ask a question about alternative histories and speculations, let me clarify the question a little:
- Were there any plans by Hitler of who would follow him if he died?
- Was there any "crisis squad" or people who were responsible in that case?
- Did they even think of that/accounted that or thought this would never happened?
- Is there any indication that this would have caused a crisis or problems/unrest in the population?
- Were there any indications by others e.g. close to Hitler that could have adopted power?
- Can one estimate how much disruption would have caused that? Nearly nothing with just someone following up or could it e.g. have shortened World War II?
So of course one cannot say what would have happened, but surely there must have been some "backup plan" or so? Or one could estimate how important he was for Nazi Germany and whether he could have been easily "replaced"…