The problem is that the Shuttle (no matter how modified) could ever go outside Earth's orbit...just wasn't made for that. Luckily, NASA's Constellation program which is replacing the Shuttle (starting up in 2015) is scalable to meet the needs for Moon missions (in 2020) as well as setting up missions to Mars (2030-2040).
China is also pushing their space program VERY aggressively, which will give the US a kick in the pants again to compete (and give our president a kick in the pants to give NASA the money they desperately need). There is even a chance that China will land men on the moon before we do in 2020.
Anyway, latest Shuttle update - External tank is now being fueled with a 95% chance of launch tonight at 9:20EDT/6:20PST.