I wrote an article on this subject that will run soon.
My belief if that if you aren't losing strength you will not lose muscle. When you are on an hypocaloric diet your body will look to dump muscle to decrease its daily energy expenditure. You must give it a darn good reason to keep it. And in my opinion suddenly using lighter weights isn't something that screams "I need to keep my muscles".
Traditionally in competitive bodybuilding a lot of people do higher reps when they cut. But that is an idea that works mostly with people using steroids and other drugs that prevent muscle loss by themselves.
Anyway, the article will go into a lot more details, look out for it soon.