Is Facebook likely to become a bank in the future?

No. Facebook in reality would never become a bank. There is just too much money, traction and domain knowledge required for Facebook to become a bank. Sure, they can buy a bank out there and there, but for Facebook to truly become a bank, they would need to then be a bank in all the territories that they operate in, and what for? What would they be doing? Dealing in Money for purposes of transfers or credits to buy stuff? They can already do that very easily by just partnering up with the likes of Western Union and have an arrangement to only handle virtual currencies on their own platform and even that is questionable.