According to the Disney Parks Blog:
In order for Mickey and Goofy to get ready for this transformation, Mulholland Madness will close October 12, and the last time guests can go for a spin on Disney’s version of Mulholland Drive is October 11.
We’ve also shared news here on the Blog about the 12-acre Cars Land expansion due in 2012. You might be interested in knowing that Bountiful Valley Farms will close on September 7 to help pave the way for Mater’s Junkyard Jamboree.