I would guess, and those who know these movies far better then me can say better then I can, that some of the movies could more logically have sequels more easily then others could. With toystory what would it be, their owner takes them to the beach during a trip there, or when he goes camping, or they move, and the toys get left behind and have to go to where their owner (not seen it in a while so don't remember the boy's name) is, or get back to their home. There may be other possibilities for a plot. Though I've not seen cars I heard it ended with a happy ending so not sure how that one could have a sequel, unless they do the same plot but using a different town and maybe do an actor car, or someone with amnesia or something like that.
