For starters, we've got the Planar Attunement system. This system is being introduced to allow progression for level 50 players, and it awards attunement experience for any activity that would normally grant you experience points. With each level of attunement experience accrued, players are awarded attunement points that can be spent in attunement trees (each associated with one of the six planes) to grant further bonuses for their characters.
Also coming to the game are the Chronicles of Telara instances, which are one- to two-player instances designed for players just getting started on progression after reaching level 50. For players looking for a bigger challenge, the team is introducing Master mode dungeons, which are much more difficult than the current tier 2 Expert dungeons. Of course, with the greater challenge comes greater rewards, such as Marks of Ascension, which allow players to purchase tier 1 raid gear.
For the PvP-minded, Accolades have been introduced into the game's Warfronts. These Accolades reward exceptional gameplay, such as getting the first kill of a match, killing a number of enemies without dying, or wiping out the entire opposing team.
The full details can be found on the official forum posts, and all of this is up and available for testing on the public test server. So what are you waiting for? Go do your duty to Telara, Ascended!
Thanks to ren54 for the tip!