It's been announced:
- Erina will become the 10th leader of MM after Mizuki graduates from the group.
- Ayumi will remain the sub-leader.
- Sakura will also be the sub-leader.
No surprise there.
The only thing that surprises me is Sakura being sub-leader. Originally, the reason to have two sub-leaders was to remove that dilemma of which member should get the role, if the second in hierarchy or the oldest who's not the leader. This time Ayumi is older than Sakura, so there's no reason to have two sub-leaders. Unless Ayumi is planning to announce graduation next.