Isaiah

Loki won't be joining 1 he is too big to even fit on the ship. 2 it may not be anyone we might have the final setup. 3 if it was going to be someone Yamato or vivi would be my guess. Yamato cover story finished like jinbe when he said he join the crew and meet them later. Also vivi was given official member status and also needs to be with someone who can help her (she is also not a princess anymore since she is wanted).