My main concern about the DHS overhaul is that they are taking out 3+ current attractions to put in the planned new stuff. So, not only do they have to make up for what is being replaced, but they have to also create the needed additional rides for the park.
And don't forget that if they take out 3 current attractions, and put in Carsland, you'll have more guests visting DHS, and ever more strain on what is left.
Also, assuming it takes them years to build Carsland, they'll be in the hole 3 attractions . . . building Carsland was OK at DCA because DCA only got about 5-6 million visits, and they had opened Mermaid and had World of Color as new offerings, and most importantly, Carsland was built on a parking lot that was not a guest area. DHS does have a yearly attendance target, after all.
LMA is sort of like the Fantasyland theatre in Disneyland, a space hog, but because it can be repurposed with new shows indefinitely, they wouldn't want to get ride of it. Wasn't residential street demolished in 2003? And LMA built in 2005? Even if they did away with the stunt show, can't see Disney junking that seating area that is very new when you realize that Videopolis/Fantasyland theater has been around since 1985.
If DHS got Carsland, I think they would build it in the parking lot while the hordes at DHS are, for the most part, blissfully unaware of the construction. The bonus would be that DHS would have Carsland, plus all of the old stuff, which could then be upgraded. If Backlot can't be fixed, then most likely it, and it alone, could be closed and used with that empty soundstage for a Pixar attraction.
Even if they built Carsland in the parking lot (and built a parking garage), it would still be so hot in the summer . . . I think that the custom-built areas of NFL are the best parts, BoG, ETwB, and 7DMT looks better than Mermaid, which was cloned and kinda doesn't fit with its queue.