C3PX said:
(as there was nothing to say the Empire was over, other than having lost their second end all be all weapon, and having lost their Emperor. If the President of the US was killed, and we lost a few of our finest battleships, it would suck big time, but the US government would be far from fallen).

If Star Wars was meant to be realistic that would be the case, but I think it's pretty clear we're meant to take it the Empire is over at the end of ROTJ.

In the SE it's all the more clear with that Gungan shouting "Wesa free!" The SE is bull, but I think there it may underline what was always the intention with ROTJ.