Han is stuck in Carbonite he isn't going anywhere and he knows that he is still there because Lando is keeping an eye on things.
Luke wants to rescue Han but he wants to do it right.
Leia wants it done yesterday (she is in love with Han and like her Father in the PT and Luke in ESB her emotional attachment has blinded her to her larger responsibilities), when she get's captured she, Han and Chewie are in immediate danger, that's when Luke turns up.