[Blackbeard D. Kuma]

It is interesting to note that it is Coby's dream to become an admiral. Having said this, it makes you wonder if one of the current admirals will retire or perhaps get kicked out for ignoring world government or marine protocol.

If the former happens, I think that Aokiji would be the one to retire, consequently allowing Coby to take his place as the new admiral. This would make sense and Aokiji would definitely deem Coby worthy of taking his place due to the fact that Coby follows his own sense of justice. Coby would be the ideal successor to Aokiji in my opinion because he is genuinely a good person that stands for what he believes is truly virtuous.

If the latter is to happen, I think that Aokiji would be the one to get kicked out and have his rank stripped from the Marines. The reason I think it would be him is for two possible scenarios. The first scenario is that I can see a situation where he is given an order from the World Government that he knows is wrong and thus refuses to do it. Not fulfilling this order would then be of a major consequence to the world government by causing them a great deal of turmoil, so as a punishment they would have Aokiji exiled from the marines force. The second scenario I can foresee is Akainu going on a massive rampage to apprehend someone the world government wants dead, but then Aokiji intervenes and prevents Akainu from completing his mission. This would greatly upset the world government and they would then take matters into their own hands by stripping Aokiji of his rank and having him disband from the marines force.

Anyways, these are two possible ways that I speculate on how Coby could possibly become an admiral within the present timeline. Moreover, if Luffy does end up getting caught when he becomes the pirate king, I think that Coby is going to be the one to catch him. If anyone is interested, please share your thoughts on this matter.