You know that as long as Lucas lives there is a good chance that Star Wars will return to the big screen, again and again and again. Next stop 3d crap, and the complete destruction of the OT. But I rant.
I think there's a stronger possibility that
Star Wars will continue on TV, in animated form (which gets closer and closer to live action quality all the time). If Lucas hangs onto
The Clone Wars writing/producing crew, the writing quality doesn't need to suffer unduly. They could continue the story past ROTS and link up with the OT (hope that doesn't strike terror into anyone's hearts).
Star Wars could continue indefinitely without jumping back to movies, but
Star Trek can't maintain its identity without jumping back to TV sooner or later. There just isn't enough breathing room for
Star Trek's indepth characters and ideas in the movie format.
The nice thing about the Trek universe is that, while the Federation is not perfect, it's shown as basically having the best interest of its citizens at heart (not just the governing elite) AND that it has STRONG guiding principles that are adhered to so strictly as to sometimes be a little WTF (Prime Directive, anyone?).
The real distinction of the Federation is that it's been artificially insulated by its writers from the dirty reality of how warfare and politics as they would play out even in the unreal context of interstellar empires (assuming all the aliens behave more or less like humans and all the empires like nations, which they do, so the same rules that applied on Earth will apply in space).
It doesn't matter if the Federation governs for the good of its citizenry and has upstanding values; it will still encounter situations where unappetizing behavior is called for, in the interests of survival. But the times
Trek has portrayed this, it hasn't come to grips with the implications but rather dropped them and scrambled away quickly.
How about replaying In the Pale Moonlight, but this time the Romulans find out what Sisko and Garak did, and use it to extort territorial concessions from the Feds, who can't reveal why they're giving up territory and displacing their own citizens? How about a storyline like the end of DS9, except this time instead of tap-dancing around the notion that the Feds won a war through genocide, the writers admit it to the audience, even if nobody within the story admits it in public?
DS9 at least has already gone dark places, but just hasn't stuck with the implications of those storylines to any extent. In the case of winning-a-war-by-genocide, the writing was so fuzzy that it was difficult to see what the intent there really was.
It would be better to have a Mulder type in there. Someone who bucks the system. Is at odds with it. Is concerned with what they do. WIth what he or she has done.
Replay Sisko & Garak from ITPM, with the Sisko character being young and naive and the Garak character of course having been around the block a few times. So as not to upset the power dynamic (and make the wiser Garak type too strong), I'd have "Garak" also be brilliant but a loose cannon who tends to be drunk on his/her own power, and "Sisko" is assigned by S31 to keep an eye on "Garak" and restrain his more outlandish tendencies. Then it becomes a tug of war over who influences whom more, as the characters evolve within each other's orbit.
Hmm, I'm starting to warm up to the S31 concept. I think there are ways to keep it within the bounds of
Star Trek after all. The bigger difference is that this is feeling like a two-person series rather than the usual ensemble.