My only question about the rumor is the time it would take to prepare a train with a new cars wrap.
Id be surprised if they took the Tron wrap off Coral before the DVD release of the movie which should be somewhere around April/May.
I believe Cars 2 will be out end of June, the wrap job would take about a month, factor in a month to restore Coral from Tron + Rehab and I'm not really sure there is enough time to run it around before Cars 2 is released.
Sure they could rehab Coral and wrap another train at the same time but that would only leave them with 9 trains going into a very long busy summer period.
Going along the same timeline as with Coral they run Tronorail around close to 6 months advertising the movie prior to its actual release, for them to do the same thing with Cars 2 that would mean a train should be getting wrapped now or within the next week or two.
I have heard a rumor about Cars 2 as well, I just don't see where they have the time to complete the job and get enough advertising out of it before the movie release like they did Tron.