Is this something that you really need done, or was it just a suggestion made by your orthodontist? Were you told that it was possible to go ahead with treatment without the operation?
I was made the same offer but refused, I decided that braces would be enough for me as I wasn't putting myself through such an operation for something that gives me no problems. If it's a problem for you, or likely to become a problem in the future then it's something that you should maybe look into. My jaw, though it's not perfect, is okay and causes me no trouble at this point in time. It could change yes, but I was advised against it by my orthodontist, it was just their job to give me more than one option even if it they didn't agree with it.
Everyone is different, some people desperately need it, and others don't. Speak to your orthodontist and discuss how much you need it, if it would be a great benefit to you. If it's just a case of having perfectly straight teeth, are you really willing to put yourself through an operation and then have to deal with what comes next? It's a serious thing for straight teeth.
Not having the operation can cause problems down the line, I can't tell you what since I was given this information around three years ago, but it's something you should discuss with your orthodontist. If you desperately need it done, then go for it, but you should always ask about other options such as just having braces, if that's not possible, and it's something you want to do, go and have the operation.