the only time i have experienced this "rebound" you speak of was when i was natural and lost a shit ton of muscle getting ready for a contest, and the second was when i quit training for 2 months then got back to it.
all my other contest, where i only lost a maximum of 12 lbs in 10 weeks (including water depletion on the day of the contest... so it's probably 9 lbs) and this contest where i lost 6 lbs INCLUDING THE WATER DEPLETION! the week before the contest i was 4 lbs below where i started 22 weeks before when i started dieting, there was no rebound what so ever. in fact, the only thing i experienced was severe bloat, constipation, and looking like shit the whole week after a contest.
if there is a "fabulous rebound", i would suggest you don't lose a lot of muscle next time.
now, to your main question about how long you wait til you start training... usually people stop training 3-5 days out of a contest, right? i don't know if that's what you do, but i stop 5 days out, and stop cardio 4 days out. the contest is usually on a saturday in the states, so, you just compete, then you go eat a nice meal after that... sunday you probably won't train, and you will still eat some good healthy food
.... by the time it's monday, you would've eaten 10 billion calories on the weekend, and rested for about a week or so without training... i think it's time you get back to the gym and you will be properly rested, and nurished.