Well, it entirely depends upon your friend and his professional profile.
He can think of a reattempt if:
However, he should thoroughly evaluate his chances of being successful in securing his place in either IIM A, B, or C. Also, will his/her profile be good enough next year? With the admission criteria changing every year, it's not advisable to drop an offer from one of the premier non-IIM B- Schools for CAT retake. The cost of dropping a year in terms of money, time, and work experience, in particular, should be thoroughly evaluated.
Drop a year only after careful consideration. Otherwise, it will be wise to join FMS and give MBA a shot.