Jerry should at least stay for one more year. Why you ask? This way they (the writers) can write episodes around stories from the past and bring back people like Baboo and a list of others. Plus there can be a show about new years eves Newmanium. All the others on the show have a year left on there contracts so theres no reason not to let these guys do their jobs. The show can work w/o Jerry. Hell, George and his parents alone can carry a series w/ The K Man, Elaine and Newman.
Just my opinion