The original thoughts were that people only want to see one stunt show during a visit to a theme park. And Disney assumed people would flock to the new, hip, edgy, cutting edge Driving show and leave the Indiana Jones show empty. Disney could then tell George "no one likes your show" and close up the theatre without too much fuss.
Things aren't working out that way. The general reaction to the new Auto show tends to be "it's okay" - the show certainly isn't attracting lots of people to the Studios. And with the fourth 'Indiana Jones' movie hovering out there in the not so distant future, Mr. Lucas isn't so fond of giving up one of the few things keeping that franshise going.
Even if the stunt show was to close, don't necessarily expect a
Disneyland/DisneySea ride to show up. Disney will not make one-off rides anymore; WDW won't see the jeep ride unless Disneyland Paris or Hong Kong Disneyland buys one as well (and therefore cover a lot of the costs). At best, WDW could see a clone of the Indiana Jones Rollercoaster from Paris or Tokyo Disneyland because it's extremely cheap.
But the biggest battle Disney/MGM Studios faces is Disney itself. Right now, if you believe the rumors, Disney considers this park to be full and complete. It's a good balance of having just enough rides to attract people without having "too many" to increase costs. That's why there's been no attempt to replace the 'Hunchback' show, the TV/Doug Live/empty theater, or all the other empty spaces. You show up without them, so why should Disney offer anything more?
...the "backstage" street scene area is pretty much wasted space.
Remember this area was supposed to be a real, working studio backlot. When the place first opened the closest you got was a quick drive by on the tram. But as Disney realized that no one is dumb enough to film on a lot in Florida, they turned the backlot into "guest" space. What little room there was soon became the 'Honey I Shrunk the Kids' area and the Muppets section.
