Hi Dopey, You may be putting the cart before the donkey.
The Fed designed QE3 and implemented it by (a) printing money (b) buying (1) Half Treasury Bonds (2) and Half Mortgage Backed Securities
As it tapers it reduces Treasury Bonds and Mortgage Backed Securities equally.
The question is : Once QE 3 is wound up will the FED withdraw the greenbacks or will it find a way of smuggling them back into the market to pay off Government debt?