Calling it now: Ryze's rework will include AP to Mana and Mana to AP
Why?
Riot specifically talked about Ryze building tankiness and gaining damage and spammability at the same time the last time they nerfed him heavily, saying in his rework that they would fix that.
This is how you fix that.
Ryze still remains the unique Mana Caster and builds Mana to gain tankiness and damage but not so much that he can just be a 4000 health 300 Armor Burst Mage