While not wanting to p*ss on anyone's bonfire, according to the Bloomberg article about this story, Visa (along with MasterCard) don't actually issue credit. They only process credit and debit card transactions. So long as people use any form of plastic instead of cash, it will continue to do well
What is interesting about the sale is that their previous owners comprised a number of the big banks. Looks (to me) like this is yet another sale of assets by the big banks to increase their capital base during these "challenging" times.
Edit:Typo