Nope, that specific title is secure. I really love calling her queen but something about the word "princess" makes it so innocent & anew for her when she started out, and she was still very young. I never see the word princess being thrown out like that other than Britney. Most of the time people are claiming gaga, Katy, & Rihanna or whoever Queen of Pop without being princess first.
Yes. She's the Pop Princess.
Beyoncé and Xtina will both be seen as legends as well, probably.
Miley, Katy, Rihanna, Lady Gaga,etc. could become pop icons but not that kind of music royalty.
Britney was embraced by Madonna and MJ so she kinda got it in the bag.