My idea is:
I'm predicting that a new vice admiral would be about 16 years old and was discovered in the past 2 years that luffy was gone, and is going to be trouble for the strawhat crew. im thinking it would be somebody with a tremendous amount of haki and possibly with a devil fruit
P.S. im going to laugh so hard if i'm right and it turns out to be Koby XD
And im predicting of a person with Ace's old Mera Mera fruit that goes against the strawhats.
once again, would be laughing if koby was also this person