In January of 2017, MasterCard will begin issuing cards starting with 2 (in addition to their existing cards which start with 5).
Starting in June 2017, merchants could be subject to hefty fees if they are found not accepting the new card numbers.
https://www.mastercard.us/en-us/issuers/get-support/2-series-bin-expansion.html
https://www.linkedin.com/pulse/mastercards-new-2-bin-scott-tivey
In order to recognize these cards, all users are recommended to upgrade to Freeside 4.1 (v4 branch) or 3.91 (v3 branch) before the end of the year.