Selena is in a good way but I don't think she will ever be considered a main pop girl in the same league as Katy Perry, Taylor Swift or Rihanna. Also she doesn't need to, I don't think pop artists need to be part of the "main pop girls" anyway, it's just a stupid tag.
And Miley... I feel like her success in the past era was basically because of all the controversy (and even with that "Adore You" failed to match WCS or WB) so I'd like to see how she can do without being controversial before judge.