That's possibly an issue. Recycling and reusing old zones, which sounds like a good ideal, is not enough to please the player base at large. A new expansion would help but.... gonna use the lolps2limitations as a scap goat. The new battle content feels poorly delivered to people. Less people participating in these means less people are around to do them for the people who would actually care to take part in the events instead of complaining about it.
I, for one, like voidwatch. I don't like how hard the drops are to obtain and sure it's not perfect, but that's how SE is gonna make their money... having us doing this crap for months, if not weeks at a time. Some one pointed out how the time limitation for older end game kept people around. But now most stuff is easily accessible that you can do stuff on your own time. Neo-dynamis, abyssea NM pops, void watch, even WoE (even though you're now waiting a whole game day instead of just the time it takes for monsters to respawn in a flux.) But it's easy to burn out on this stuff now.
But really, aside from another expansion, what would you have them do to keep people interested in playing the game? What will do you after you get the equipment and weapons you want within the week, if not within the month?