The thing is, Marquis Teague was a complete after thought in preseason until Derrick Rose missed a game. The Bulls didn't even look like they were trying to see what he could do before then. He was getting less playing time than Erik Murphy who, IMO, likely doesn't belong in the NBA.
When asked about the bench at media day, Marquis Teague's name was not mentioned by Tom Thibodeau.
So while the theory of Teague slotting in as a future backup PG makes sense. My guess is the Bulls have seen enough where they aren't going to chance it. They're in win now mode and will likely look to bring back Hinrich if he has a successful season rather than take a risk on Teague playing well for them given what they've seen.