[marty]

Well, I suppose Utada or Ayu (how isn't she on this, wasn't evolution like, a Japanese anthem or something?!) would be the logical choice, even if I would prefer Namie. Also, Namie already performed oversea, I don't really know about others, but whatever.
But, since groups are so tipical and famous in Japan, I guess a band would do as well. In the end, it should be what represents Japan best. There's still a looooot of time after all.