Yesterday evening ArenaNet teases what is expected to be the Mesmer specialization: the Chronomancer. From the Guild Wars 2: Heart Of Thorns launch trailer, it's clear that the shield wielding mesmer has a grasp on time, with one of the skills used clearly showing a clock and a delayed action. It was also confirmed in the recent Q&A and I did with Jon Peters that the Mesmer specialization would offer different ways to shatter. Finally, it was also said that the first specialization to be revealed this week wouldn't be the Druid. To then drop a picture of the Mesmer pretty much seals the deal. 

As to how the Chronomancer will play, no one really knows. I suspect however there will be an emphasis on high burst like the existing Mesmer but with a much greater focus on area of effect. One of the weaknesses of the Mesmer is its inability to deal high AOE damage, but also that it can't really be played as a spellcaster and the profession generally struggles in a PvE environment. 

I'll keep you posted on further details.