Basically, this article makes an argument that the 5th Amendment (in its current interpretation) has already implicitly repealed the natural-born citizen requirement for the U.S. Presidency:
http://repository.jmls.edu/cgi/viewcontent.cgi?article=1287&context=lawreviewAs for me, I voted Yes. After all, if one embraces the idea of a "Living Constitution" (as I myself lean in favor of doing), then I see absolutely no reason as to why exactly earlier parts of the U.S. Constitution should be incapable of being implicitly repealed by later parts of the U.S. Constitution.