I think your concerns sound like they are two fold.

Are you worried your interest in ffxiv won't last and your time will be wasted? Even if the populations suffers a nosedive you still have years worth of updates.
No game lasts forever. (Yes, even dragon's crown...)

If you want to come away with something, try making friends with other players in your time zone or area.

Or are you concerned about the time you spend on games in general?
Pick up something else or focus on another aspect of your life. The game will be here when you get back.