Several USPS changes are scheduled to go into effect on January 17, 2016. Shipping service rates are increasing (Pitney Bowes released a video detailing the price changes) and the USPS API is being updated to remove several flat rate box services and to reflect that “Standard Post” is being renamed “Retail Ground.” Magento will be including these updates in an upcoming release and patch. 

Updated January 20, 2016:

A new patch (SUPEE-7616) is now available for Magento Enterprise and Community Editions. Additionally, the new Enterprise Edition, Enterprise Edition 2.0.1, Community Edition, and Community Edition 2.0.1 releases all include the USPS changes. The patches and releases are available from the Partner Portal, My Account, and Community Edition Download Page.