The story as I understand it:

Disney got the rights to this movie in the early 1980's. John Lasseter, employed by Disney but quite miserable, put together a combination CGI/Animated test of a Where the Wild Things Are scene, showing how the two could work together. Disney soundly rejected it, and later Lasseter was invited to try working with Pixar, which he accepted handily and started work on "Andrew and Wally B".

No doubt this property has been jangling around Hollywood for years and years, and now has a pretty interesting director attached to it. How much Tom Hanks brings to the concept, I'll never know.