ALTHOUGH George Lucas has more or less promised his public a nine-part "Star Wars" cycle, there's no reason to hold him to i;t; the resources developed by the Lucas organization might be invested far more freshly in new endeavors. Lucas has changed his mind about other things, including the title "Return of the Jedi" (which had been "Revenge of the Jedi"), and he ought to change his mind about this.

To the just-completed trilogy, Lucas had planned to add a second trilogy set a generation earlier, and a third set a generation later. Probably to that end, he has avoided following through on certain mysteries left conspicuously unresolved at the end of "The Empire Strikes Back."

It's amusing to recall how many once-plausible possibilities in these movies have become obsolete or untenable. Remember the Clone Wars mentioned by Obi-Wan Kenobi in the first movie? On a number of occasions Lucas indicated that this conflict was a key to the solution of the mysteries posed in "The Empire Strikes Back." But as events unfold in "Jedi," the Clone Wars fade to insignificance. Ironically, Lucas may have ended up rejecting the logic of some of his own clues because fans had already published clever speculations about the "Empire" enigmas in the intervening years. That's only one of the liabilities created by keeping a narrative dangling for three years.

Back in 1977, during an extensive interview with Rolling Stone, Lucas outlined the prospective first trilogy as follows: "It's about Ben and Luke's father and Vader when they are young Jedi knights. But Vader kills Luke's father, then Ben and Vader have a confrontation, just like they have in 'Star Wars,' and Ben almost kills Vader. As a matter of fact, he falls into a volcanic pit and gets fried and is one destroyed being." Without going into detail, suffice it to say that the completed trilogy would now require major revisions to that original concept. And the longer Lucas tries to sustain the saga, the greater the chances of being forced into tight and ultimately suffocating plot corners.

Why string out the story, particularly when it threatens to be a self-defeating exercise? Surely the triple-duty stimulation of "Star Wars," "The Empire Strikes Back" and "Return of the Jedi" is sufficient to last moviegoers for the rest of the century or so. Does anyone really want to see inertia finally catch up with George Lucas on that long-ago and faraway galaxy? Does it really matter if the chapters of this saga end up being numbered 4, 5 and 6 instead of 1, 2 and 3?