First of all, Pixar knew that Toy Story 2 would not satisfy the terms and agreements that had been outlined by the current (extant) contract between the two companies for the mutually agreed upon number of original movies. When Toy Story 2 was being developed as a straight-to-video property and...
THE BOTTOM LINE is that Disney owns the rights to Toy Story, Monsters Inc., Bug's Life, and Finding Nemo. (Not to mention the two unreleased Disney/Pixar collaboration movies that will be released over the course of the next year-and-a-half.) It would be the height of naiveté' to expect...