Apparently all three manufacturers in LMP1 are in favor of retaining the current set of rules beyond 2017 and are pushing for no changes in the forseeable future to keep the costs down.
http://www.motorsport-total.com/wec/...-15090302.html
Sounds reasonable to me, long-term stability is always a good thing. Whether the ACO & FIA agrees probably depends on whether there's commitment from a new manufacturer to join in 2017 if the rules change.