I'm not sure I've heard of people using hypnosis to learn things before . . . frankly, I'm a bit skeptical that it's effective at all. Most stage shows will have the assistants weeding out a few people who don't respond to hypnosis much. I've heard it said you have to let yourself be hypnotized, that it can't just be forced on you.
With all that said, I'd suggest that a chess player would want to undergo hypnosis to improve concentration or overcome mental hangups about the game (say, excessive fear of losing or impulsiveness), or even to help them have a better attitude about practicing. Opening memorization is okay, but you'd be better off studying a lot of master games or something to get the ideas behind key positions, rather than trying to spit things out from memory. You don't want to set yourself up to be brought down by one theoretical novelty.
If you have to "let yourself" be hypnotized, how is that any different from "it works only if you believe it does?" My 2 cents is it's a tool therapists use to get patients to drop their guard by using some pretense that exploits pop culture beliefs. Dropping one's guard is what's working, not the hypnosis itself.
http://youtu.be/WfhXQDPpf_o
Science !