There have been rumors that Curb Your Enthusiasm could return for another season, but Larry David doesn't seem particularly interested. Talking to Grantland David said that the odds against another season are 6 to 1 - so while he's not ruling it out entirely, it seems unlikely.
What he is ruling out is a Curb finale. When Bill Simmons floats the idea of a 90 minute Curb wrap-up movie, David explained that after the Seinfeld finale he doesn't think he'll ever wrap anything up again on TV.
I think the thing about finales is everybody writes their own finale in their head, whereas if they just tune in during the week to a normal show, they’re surprised by what’s going on. They haven’t written it beforehand, they don’t know what the show is. But for a finale, they go, “Oh, well this should happen to George, and Jerry and Elaine should get together,” and all that. They’ve already written it, and often they’re disappointed, because it’s not what they wrote.
He's right, of course. It's almost impossible for a TV show to have a finale that satisfies everyone. Even when everybody likes the finale - like Breaking Bad - there are still people trying to write their own versions of it (there are people who think the finale of that show is a dream). It's the curse of longform storytelling - yes, you have all this space to create something with depth that people can return to again and again, but that length gives viewers lots of time to think ahead to your ending, and to try to outsmart you. If the ending is too close to the obvious one - ie, it follows the set up of the story to its logical, strong conclusion - people will complain. If it's too much of a surprise people will feel unsatisfied. I'm always amazed that people hate the ending of Battlestar Galactica, which wraps up thematic elements present from the very first hour of the series but which I guess everybody forgot (it was always about religion, guys!).
Then again, the M*A*S*H finale was awesome and everybody liked it, so you can win every now and again.