I'd love for a Toy Story 4 to be developed! But I don't think it would be the same without Andy, and since he moved to college and gave his toys to one of his mums' friends daughter, I don't think they'd make another. But I suppose that it's a possibility and could happen in the future.
Toy story 4 will not be good, making many movies under the same title makes it sick.. Not many people will watch it
It's quite a miracle that after so many years they could make Toy Story 3 so good. Sadly though, I don't believe the run can extend to a fourth movie so they should quit while they're ahead. I've watched too many bad sequels of movies to want a fourth part to my favorite animated movie of all time.
I think if they are going to do a 4th Toy Story it is going to be something spectacular for people to watch.