According to IMDB, this is the story they were going to tell:
Entertainment Weekly published an article that said the original plot for Toy Story 3 was going to be about Buzz Lightyear having a defect. Buzz would then be shipped to Taiwan to be fixed, but the other toys find out that the toy company is just replacing the broken Buzz toys with new ones, so they ship themselves to Taiwan to rescue him.Basically, it's just a knockoff of Toy Story 2. Same basic idea, one of the gang is missing and the other toys go after him, with a foreign angle. To be fair, there could have been a nice message about the worth of the individual in a cookie-cutter world, but it's just not very bold or ground-breaking.
When Disney acquired Pixar, they ditched the concept above and started over with Pixar in charge. They still did Toy Story 3, which is currently doing great business in theatres, but with a very different story.
Rather than a retread or a safe adventure, Toy Story 3 deals with the harsh reality we all knew was in the toys' futures when we first met them; Andy would eventually grow up and lose interest in them. The toys would either be sold, thrown out or boxed up. Toy Story 3 tells that story and what follows is all about loss, growing apart, and obsolescence. It's stunning, moving, dark, funny and wonderful.
Given the mature themes of Wall-E and UP, it's not surprising that Pixar would choose to continue examining mature themes. But that they would examine those themes in the context of their most kid-friendly, beloved universe is incredible.
And that's why Pixar is full of genius and the best movie studio in the world.