Boras would be an idiot to negotiate before free agency. He can always come back and sign with Cincinnati if Choo insists, but why would they limit themselves. He's played some 10 years being traded from one place to another with losing teams. This is his first time being able to dictate where he wants to play. I doubt they will easily sign it away.
Maybe we could have signed him long term when we traded for him. Maybe we could have gotten 5 for 80. Now the time has probably passed. He seems back in his 2008-10 form. Barring injury or complete collapse he's going to get 100/120+ somewhere.