DIsney has updated that the addition of Lightning McQueen to Lights, Motors, Action! Extreme Stunt show will take place "later this summer". We've heard Lightning's debut has been delayed again because of issues with the car and having to be sent back for further work to fix some aesthetic issues.
Lightning's role will replace that of Herbie the Love Bug and will feature a new vignette between stunts that features Lightning helping Tow Mater and a tie in to the upcoming Cars 2 film.
In addition, the meet-n-greet area is still under construction but will eventually change from Luigi's Garage theme to "the Winner’s Circle", where the area will be adorned with "larger-than-life trophies and posters that depict famous races from around the world".
The Lightning McQueen addition has already happened for a few months in Disneyland Paris, so expect to see Lightning in the next few months when the problems with his look are fixed.