They will have to become sexy and bad if they want long term careers, look at Britney, Xtina and Justin, you can't stand family friendly forever.
You can see Miley is even beginning to sex up her act, in Europe anyway, where she is legal.
Anyone like South Park? One of the episodes from the last season was about the Jonas Brothers and a bad ass Mickey Mouse said that the Jonas Brothers wear purity rings so that Disney can sell sex to little girls. As he said, "If we make posters with little girls reaching for your junk, you've gotta wear purity rings or else Disney looks baaaaaaaaaaaaaaad."