The director of Toy Story 3, Lee Unkrich has confirmed that Toy Story 3 will not be the last time we see the Toy Story characters. Unkrich says:
Well, I really tried my best to end the story of Andy and his toys and bring that story to a close in a really nice way at the end of this film. That being said, we know that people love the characters, love Woody and Buzz, and would hate to say good-bye to them completely. I don’t know that there would ever be a ‘[Toy Story] 4.’ We don’t have any plans for one — but we are trying to find ways to keep the characters alive. We have announced we’re going to do a short film in front of ‘Cars 2′ that uses the ‘Toy Story’ characters. We’re going to keep them alive; they’re not going away forever.