how big ripple can go....
It's just a rumor people are speaking over the internet. There are a reason why xrp cannot be used in banks over there long term.
Xrp is a centralized coin issues by ripple labs. The prices are fluctuating a lot on an hourly basis. Banks are not in the game of gambling and predicting how much transfers of funds will cost.
Swift is used solely exclusively by banks to message and perform fund transfers. Xrp is being traded in a daily basis like fish in the market. Why would banks be queuing at the market with you guys to buy xrp to perform customer transactions? Do you think when a customer performs an overseas find transfer, the bank is going to buy xrp and send it over to your destination? A high security bank is not going to use the same wallet, coins and application use by Jack from his basement to send $10,000.
There are no actual money transferred physically or logically. Fund transfers between banks using Swift is via updating of ledger. For example, UBS in UK is sending money to BOA in NY. UBS informs BoA that they need to use $100,000,000, so UBS requests BoA to credit their local account HSBC account with 100 million dollars. In return, UBS will give BoA $100,000,000 credit in their UK account. There are no need for actual transfers on tokens that fluctuate inconsistently every minute. The bank cannot take such risk on customer funds and the laws do not allow for it.
If anything, the banks will probably use ripple labs technology or software as a ledger to keep track of funds instead of xrp. The ledger will be a separate thing altogether from xrp. The technology is good, but definitely not the tokens. The only possibility is banks using a single ledger made by ripple software, but this ledger will be exclusively for banks alone and not open to the public. Central banks will need to check from time to time and govern the rules surrounding transfers of funds. They cannot afford to let banks mess up everything and run on the public ledger where it's hard to trace, using a token so unreliable and unprofessional. Also, banks exposed to xrp is also exposed to manipulation. Xrp price will eventually die down once people start to use logic and come back to reality. Banks collaborating with ripple are using their software, not xrp. Money transfers by MoneyGram are using xrp, but once they get burn by price fluctuation like the crash from 2 days ago, they too, will abandon xrp tokens and settle for the software instead.