I am almost 100% positive that SM in DL is not going to go upside down. I believe the new track is going to be very similar to the old track, as are the cars. There is some talk about different lighting schemes so you get a different effect during the day than at night. The soundsystem is supposed to be state of the art. But I do not believe it is going upside down.
I think it's been awhile since SM at WDW went down for a rehab, so I'm sure at some point it will happen, but more for the general clean up/fix up rehab. There hasn't been any rumor that I've read stating that it's going to be gutted like DL.
