According to the Champion Update schedule, Tank Update is next after Galio's rework

I have a few questions regarding the Tank Update:

1. What exactly is the Tank Update's aim?

2. Is this a different one from the Cinderhulk Meta we used to had 2 years ago?

3. Who are the 6 main champions selected for the update?

4. Wasn't the Diver Update next in line? (I apologize if it were myself for not keeping track.)