I don't think that banks need Ripple and I don't think that any bank will use Ripple. Even if banks begin to use blockchain or tangle(IOTA) for transfer of money why would they use ripple, only to make the owners maybe the richest persons in the world. If I was a bank owner and I wanted to utilize crypto currencies I would prefer to hire developers to make my own blockchain, with my own coins or if we are looking at using a single token between all banks we will be looking for decentralized private asset between all banks and not someones coin which we will have to buy.