Well, he clearly is not going to maintain an 88% LOB rate or allow home runs only on only 3% of his flyballs. I think a "healthy" Ben Sheets also threw 2-3 MPH faster.
I actually think what we're seeing is mid-30s Mike Mussina - heavily reliant on offspeed pitches and command, really good pitcher. So yeah, I wouldn't be surprised if the new Ben Sheets was a 4 win pitcher over 200 innings.