I haven't heard a word if Coupling is coming back, but if it doesn't this is definately a very high note to end the series on.
Its happy endings all round with Susan having the baby and after the baby boy looks into Steve's eyes you get the impression that he is ready to grow up and that he is a changed man.
Sally has found out that Patrick has slept with Jane, but Patrick proposes to Sally and everything turn out fine and Dandy!
Oliver, all ready for sex with Jane has a fair bit of trouble getting Jane's attention to let him into her house. It seems like ages but in one of the funniest moments of the episode Jane points out that he was waiting for only 5 minutes.
Jane admits to Steve that she is finally completely over him and ready to start a relationship with Oliver.
So everything seems to be wrapped up nicely for what has been a brilliant comedy. Even when Jeff left and Oliver arrived the show didn't lose much of its quality. (Although no-one will ever compare to Jeff!)
Its a great note to end on and as much as I would love to see a fifth season I can't see them coming back.