Head coaching really doesn't have a lot to do with playcalling, but I think his playcalling would be a lot better if he had a dependable QB. You had the sense watching this game that Tony could turn the ball over at any moment; a great many of his completions were easy reads.
Parcells said they had to restrict their playbook because of Tony's tendency to lay it out there...and Romo hasn't shown any improvement in this area since then.
To answer the question, I don't know how good of a motivator he is...I've read he's the kind of guy who will call guys to task if they don't play well...but I thought the whole team played hard against a very physical Steelers team. Regardless of who the head coach is next year, Dallas would be foolish to not keep looking at QB's in mid round picks until they hit on one. Romo will suffice until then.