Rondos short jumper has improved, he is like alot of players , can hit a shot quick, but when he has all day to look and think about it , he fails. Rondo can hit the jumper where the motion is fluid.....ROndo is not a standstill marksman like PP . Thats why he can't hit a free throw. He stands there and the natural mechanics fall apart. When he doen't have time to think or aim , he makes amazing shots.
So , I think Rondos pull up and release jumper will continue to get bettter. Free throws is practice thing , he needs to stand and shoot 1000's a week , till the shot become natural. Unless he's willing to practice for hours and hours on end , no he won't get alot better. He'll have to actual practice ...and not rely on natural ability.