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.
Not an answer. Rewards are all well and good, but that isnt future proofing. Future proofing is going to have to be adapting it to be SOLOABLE, at this moment Bozja is NOT soloable, Eureka needs, as has been suggested, a mega - echo so the harder mobs can be managed.

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
....and exactly how do people get help in doing these? Duty finder is fine, a 3 - 5 hr queue because no one wants to do it is a problem.