Definitely seems as though Aya will be the next successor to the sword. She could act as an oracle to lead the club to the top and more.
Just because they've seen visions of the future doesn't mean it's going to be set that way. Shin kept seeing his future and even he ended up slightly changing it.
Dunno why you keep getting Maya and Aya confused, but Aya has been able to see the future before. The time she was fighting in the bowling alley, the time she knew that Nagi was going to confess he liked Maya for the first time, and the time she and Nagi chased after those brothers who attempted to kidnap the little boy on their motorcycles while she was riding the scooter.
In the end I bet Aya is going to be the person who is able to change everything.