You don't have to be blonde to be/become America's sweetheart. Just ask Gabby Douglas or Carly Patterson.
While a win would certainly bolster figure skating's popularity, I don't see her or Wagner as a game changer. Gold hasn't dominated the field thus far (like Kwan/Cohen had done) and has yet to even win internationally (not just Worlds - anything). It's a bit cart before the horse to say even with an Olympic win Gracie will somehow cause this great shift in the landscape of American figure skating. But one can always hope.