The standard used on credit and other cards - the Issuer Identification Number (IIN) - is changing because we are running out.
The first six digits is always found at the beginning of each 12-digit string of numbers in a credit card number, but it's also used on many other types of cards that require such a numbering system. The IIN identifies the institution that issued the card.
The current version of the card is a fixed length, with the rest of the number being a variable-length number, ranging from not eight, but 10 to 19 digits. There are so many card issuers now that the first six digits is being revised to be eight digits, with the following number remaining as it is, with eight to 19 digits.
The regulatory bodies that approve such behind-the-scenes items has had its members approve the change, which will come into effect in 2017.
What does this mean?
For most of us, nothing much except longer numbers on cards. For card issuers, it means revising new cards and card numbers, with regulations including that the second set of numbers must be a minimum of 10 digits. Existing numbers will continue to be used, but will eventually be blocked into eight-digit IINs. Most issuers won't need that many, so will return the numbers back to the regulatory authority.