Today NASA announced that the K2 mission is officially extended, based on a recommendation from NASA's Astrophysics Division's 2016 Senior Review of operating missions. The extension includes funding for three additional years plus a closeout period. K2 science operations will therefore be covered beyond when the on-board fuel is fully depleted, anticipated to be sometime in 2018.
Details about the recommendation can be found in the 2016 Senior Review report. In particular, the report noted that "...with a very efficient GO program, the project includes worldwide participation covering every continent except Antarctica. The GO program is recognized as a major reason for the wealth of new scientific results."
For an overview of the K2 mission's current status, check out the latest Mission Manager update.