Christina Aguilera is absolutely out of the question.
I'm going with Adele. She's the only big-voiced artist that has not released an album in year
s. For something to "come out of nowhere" and make a splash, there needs to be legitimate anticipation from the public and quiet on the side of the artist.
Also, Adele is young enough to be intrigued by new/Beyoncé-treaded "stratagies" but still an "old soul" enough to not fuss over things like streaming and Spotify.