An official employee of Autodesk, Chris Cheung, posted a comment on the SKP forum that development has been underway for a Universal Binary and is scheduled for release (as a Beta) at the end of the year.

"My goal is to keep Sketchbook as a standalone and grow the product without degrading the feel and usability of the original releases.

I am aware of the Mac Intel issues and that is one of our key goals moving forward (platforms & OS). I cannot say specifically what will be in the next release yet, but having you on the beta program would be a great help. I've had a huge outpour of support for taking over the project and, honestly, we are really excited about the future of the product."

-Chris Cheung