The official page for Test Track on the Walt Disney World website was updated over the last few days and now has what appears to be some concept art for the new Test Track, sponsored by Chevrolet. The artwork doesnt show much other than that the same (or at least a very similar) ride cars will be used. You can view the artwork below, or visit the offical page to view it in full.
Test Track is scheduled to re-open on October 1st, the same day as Epcot's 30th Anniversary.