I agree with those who have said it should be another luchador who retires him, that is only proper and it should only go that way if it is what Rey wants. I think above all what Rey wants is what should be. If he wants to hand pick the person who he has his last series of matches with, so be it. I've always given him a lot of hell for being the "ultimate underdog" and beating so many opponents that I felt he should never have beaten, and holding the WHC when I felt he should be nowhere near it. However, I do respect him quite a great deal, I WAS a HUGE fan years ago and still feel that in me at times, and I think it would only be right to let someone like him who has given so much to professional wrestling decide how he ends his career.
I will go as far as to say that I don't think he should lose on his way out the way most do. I think he should just barely win his last match and the story your telling in the ring be part of the real life story, that his body is breaking down, he's losing a step, he's not the young man he once was, the spirit is willing but the body is not, and have him take everything he's got to win this last big match after a dozen near falls, taking a lot of damage, and once again overcoming a seemingly insurmountable set of odds. That after all, is the Rey Mysterio story.