The BBC has a good FAQ on the eurozone’s banking union. It covers all the bases answering questions such as: What is the “banking union”, What powers will the supervisor have?, among others.
Regarding the timing of the union they write:
When will all this happen?
The eurozone governments want to have the legal framework for the common banking supervisor in place by 1 January 2013.
The ECB will then have up to 12 months to put in place its new supervisory department, and take over active duties by 1 January 2014.
Some kind of common resolution arrangement should also be in place by then, backed by the eurozone’s bailout fund.
In order to keep to this schedule, the legal framework will need to be designed in a way that avoids the need for a change to existing European treaties.
A treaty change would open a whole new can of worms – it would need to be negotiated with all the EU governments, including the awkward UK. And it would then need to be ratified by all of the EU parliaments.