On October 15th, NHTSA and EPA published a joint rule making which set the GHG and CAFE standards between 2017 to 2025. See http://1.usa.gov/Sgh41d.
(a correction was published on October 18th – http://1.usa.gov/SgiEjI)
UPDATE: A further correction was published on November 16th – http://1.usa.gov/SxHmcz
Details on previous stages of this rulemaking can be found on my blog at: https://vehiclelegislation.wordpress.com/2012/01/16/2017my-ghg-and-cafe-extension-of-comment-period/
CAFE: The first phase, from MYs 2017–2021, includes final standards that are projected to require, on an average industry fleet wide basis, a range from 40.3–41.0 mpg in MY 2021. NHTSA are only authorised to publish 5 years in a single rule making so 2022-2025 will be published in a separate action.
EPA is establishing standards that are projected to require, on an average industry fleet wide basis, 163 grams / mile of carbon dioxide (CO2) in model year 2025, which is equivalent to 54.5 mpg if this level were achieved solely through improvements in fuel