Well, FWIW (and that's not much), I agree with the assertion that Shaw will not overtake Washington once he gets game experience. He is a more elusive and dangerous runner than JS, and tends to make better use of the guys around him.
IMO, there are two areas in which JS is superior to TW: First, game experience, and second, ball handling. Game experience will take care of itself soon enough. TW drops or bobbles a significant amount of snaps, and that is a problem. Does he have smallish hands? Is the switching from center to center bothering him? Is he nervous? What is the deal? If this can be remedied, then we have ourselves a serious 2nd string QB. I think wiht the number of reps he will get having to be ready at any moment that these things will resolve.
Shaw is a tough, tough, young man, and I'm proud of what he did last year, and hope he can return to the rotation this fall. His presence would give us 2 very good options (no pun intended) behind Josh. In short, we need him, but we're not sunk without him at this point.