Nintendo World were able to conduct an interview with the director of the Kingdom Hearts series, Tetsuya Nomura. Here, Nomura revealed that he is considering the possibility of Pixar characters being included in the future of the Kingdom Hearts series. The exact quote is below.
Tetsuya Nomura, E3 2010 interview.
“I am aware of the fan requests for Pixar characters,” said the Square Enix director. “I will do my best. Maybe one day Pixar characters will be featured in the Kingdom Hearts series.”