BBC has an article that confirms the slip of ExoMars to 2018.
The article also has more detail on the emerging roadmap proposal:
2016: European orbiter to follow up on trace gas discoveries and act as communications relay for future missions. A small surface package might be included. NASA to launch.
2018 (a very favorable launch year): ExoMars with NASA's skycrane entry and descent system and a second MER-class rover (presumably from NASA). These rovers could target any areas of methane or other trace gas emissions. NASA to launch.
2020: A joint ESA-NASA network mission.
Editorial Thoughts: This plan makes sense to me. It leverages past investments in technology and gives the designers of the ExoMars mission the chance to learn from the Mars Science Laboratory (MSL) mission. A precursor network lander in 2016 also makes sense as it allows a test of technologies and instruments for carrying out seismic studies.
It is disappointing, of course, to have ExoMars delayed until 2018.
Resources: BBC article http://news.bbc.co.uk/2/hi/science/nature/8168954.stm