I like the theory, but I dont' think that it will work out that way robertpcx.
I thnk that that the debt will stay with Wormtail, and then, at some point later in the books, wormtail will ahve to do something that will cause harry's death, and he won't be able to... as harry spared his life once... something along those lines!
Maybe Voldie will almost totally kill Harry doing somehting or other, and tell Wormtail to dinish it off, and leave *as bad guys always do in movies, especially James Bond!!!

* and then womrtail will spare Harry, Voldie will think he's dead....well, etc etc!
Did that make sense???
*maybe I' ve just seen too many JBond movies!

*