When Steve leaves the team its not clear who he leaves in charge. In my opinion there are 3 possible options:
Danny: He is the second-in-command from day one and he is the person Steve trust the most.
Lincoln: He is the one Steve asks to take care of the team when he goes and the most similar to him.
Tani: In "The future is in the past" she is seen by Danny as the future Five-0 Captain and she is young and talented.
Who do you think and who do you prefer to be the new leader?