I think that the new new admiral will not be a vice-captain that was promoted but a completely new character..
His appearance: His colour will be green, he will be a bit shorter than the other admirals and much younger 20-30 years old. His hair will be very long and hold them with a bun..
Character: He will be more like akainu that follows Absolute Justice and ruthless on pirates and even marines.. He will be gettin angry by EVERYTHING and will admire and follow Sakazuki..
Powers:Some badass logia user just like the others, maybe electricity but then luffy will not be affectes so no, maybe wood and could control trees as well(Senju Hashirama xD), blood ,air or whatever, Oda will surprise us for sure..xd
So what do you think guys, what's your ideas and what do u think of mine's.. ^.^