I think I would wait and let him make that descision himself. I say this because he seems to be attached to it already. At this age, he might not be ready to make that choice and have it gone forever, or really understand that it would be gone forever. My point of view is just wanting to make is easier on him and make sure he knows exactly what he is deciding to do. As for the teasing, if this is why he wants to do it later, let him. I don't agree with everyone else, I think they are looking at it from a mother's/adult's perspective. I think there are many other things and situations in life that will prove how strong you are and what kind of person you are. If having something removed helps make childhood easier, than let him have that! Sure, people tease about anything, but if taking that away in the future will make him feel better about himself, go for it. Don't sentence him to a childhood of "being strong" and realizing that people can be mean, he will get that along the way from other things anyway.
My son had a strawberry mark under his eye after birth. We were some of the lucky ones in that it went away by the age of 3. Even so young, other toddlers would point to his eye when they met him and I was so happy it faded. I would never have gone in and had it removed on my own. I would have waiting for it to be his decision. If he wanted to keep it, then I would have said all the supportive things the other posters have been saying. However, if he wanted it gone, I would do that for him in a heartbeat. I don't think it is teaching him the wrong lesson! you only get one childhood, I just would have made sure he remembered who his friends were before he had it removed!