It is not out of the question. There were talks for the Soviets to join
http://en.wikipedia.org/wiki/German%E2%80%93Soviet_Axis_talksHitler's two biggest mistakes were invading the Soviet Union and declaring war in the USA (the Axis agreement didn't require that, Japan never declared war on the USSR for example). If he avoided both of those then it is likely that Germany could have won the war in Europe. If Japan could have been dissuaded from attacking the US then America might not have grown to become the dominant super-power it is today.
