There's a lot of potential ways to breathe new life into older content. The easiest option would be to make use of the carrot on a stick feature - periodically adding new rewards to vendors in older content to funnel players there. This could include minions, mounts, glamour, emotes and housing furniture to suit a variety of player tastes.

Adding the dungeon and raid duties required to advance through the Bozja storyline to the duty finder as another poster pointed out is also a great way to future proof the place.