From what I have read, only the engines would come back. There are a couple of advantages to leaving the cannister in space. One is that you don't waste power launching mass that has to return to Earth. The "sausage" doesn't have to have the extra weight of heat shields to reenter the atmosphere.
The space shuttle weighs about 250,000 pounds plus it can carry a cargo of 50,000 to 60,000 pounds. If the space shuttle SRBs, fuel tank, and main engines were used to send up a non-returnable payload, NASA could launch 300,000 pounds of cargo into orbit in one launch. That means one cargo mission could replace six manned launches to supply the International Space Station. When you consider that we are averaging a shuttle lost per 50 missions, and the space station is expected to take 50 space shuttle missions, it is quite probable we could lose aother shuttle just hauling up modules for the space station.
Instead of risking 50 crews lifting modules up to the space station we could haul up the same equipment in six or seven cargo missions with hardware that we already have.
No question something is going to have to be done to enhance the shuttle fleet survivability if NASA wants to stick with it. These things were designed to be used 100 times. Columbia made it to a quarter of that, Challenger even less. We're going to run out of these things if this keeps up. And I can't see Congress appropriating and more funds to build more orbiters that keep getting lost when the whole idea was that they would not be lost. Too much pressure to spend money elsewhere (e.g., entitlements).