I think many are underselling Rondo. He still can't shoot and teams will still sag off him and disrupt the offense for the rest of the team but this is actually a perfect team for him. He will play enough defense when he needs to I predict. Davis will still be anchoring the defense.
Think back to when Rondo was at his best. He had Pierce, Allen, and Garnett to feed the ball to. Now he has LeBron, Davis, and Cousins. I don't think Rondo will be the problem with this team. He will be fine. I don't see him as a star and he will battle injuries along the way like everyone else on this team but he will be a solid distributor of the ball who won't worry about taking shots. He will be perfectly happy to push the ball up the court, and then dribble around and look to rack up assists, just what the big guns want.