Ah but here is the rub,
The DHS theme is changing with opening of TSL and SWE, and they want another huge people eater to help with SWE crowds. By alot of reports, GMR is in need of a ton of work, and while Disney could afford to fix it, they have decided to move to a new ride system that is easier and cheaper to maintain.
Most rumor are all over on this, one choice is WDWMagic.com, but alot of sites have this rumor.
Per Martin(a very reliable insider) this ride will close this fall, to start work.