Hitler's plan was to flee to Austria (using an automobile, I think) and continue the war from there. The USSR bocked the road that Hitler was going to take, so he had to stay in Berlin. If he had left two days earlier, he could have made it. I read about it in the excellent book "The Unknown War." What would he have done afterwards? I personally think he might have gone to Switzerland or South America, and from there he might move around as frequently as possible to try to avoid capture if recognized. But I have nothing to back that up with.