#3 Asuka
One should never exclude the possibility of a repeat winner when it comes to Royal Rumble matches. Although Asuka has been booked like an absolute idiot over the past year and has lost almost all her momentum, her recent battle royal win could be seen as a ray of hope.
If Charlotte Flair is not facing Becky Lynch at Wrestlemania, there is no other babyface on the Smackdown roster more fit for the role. Also, it may happen that Charlotte becomes the champ before Wrestlemania, and WWE see Asuka as a good opponent, owing to the excellent match the two had last year.
This would, of course, mean that Becky would be seen only in the battle royal, which would cause enormous fan outrage, but we can never trust WWE to listen to their fans over sticking to their plans.