Ive jsut watched The Return of the Jedi (episode 6), and at the end all of the major players from the Dark Side are killed. Where is the Dark Side threat going to come from in episodes 7, 8 and 9?
Basically, it's not. George Lucas has said that he won't be making any more Star Wars films after the three prequels. The stories have been carried on in books, with various other threats to the New Republic, if you're interested.
I can't remember exactly what happened in the last film, so you can metaphorically slap my wrist if you like but if there were another film surely it would focus on the internal conflict among the good guys. People can remain focused on a particular cause for as long as necessary but afterwards everyone has their own ideas about how things should be run leading to internal strife.
Although George Lucas has no plans to actually film 7, 8 and 9 he does have the plots mapped out. He has said he would consider making them with someone else. It is rumoured that Luke goes over to the dark side. Stav - you have to remember the dark side is in everyone - not just the baddies!. Completely agree with you though, Snotmonkey, those three little words also sprang to my mind when I heard them!