WvW updates definitely. It was one of the major things that was/is genuinely unique to GW2 that gives a good grab-bag of both lite PvE alongside both lite and more hardcore PvP fights. If handled correctly, it has a little bit for everyone while having the added bonus of having both direct and indirect interactions/effects on other players. That dynamic component of player-player interaction can serve as a near infinite wellspring of interesting content/experiences with only minor additions here and there to shake up the meta, WAY less in the long term than what would have to be put into making the normal PvE content interesting long-term.
Right now it's marred by a long list of problems. Sub-optimal profession balance, stale map metas, bots/hackers, general performance issues during larger battles (even on fairly modern PCs), lag problems (which _has_ gotten better recently, but the standard for tolerable latency is higher in PvP than it is in PvE), and just a general lack of content additions to make people come back and see what's changed; WvW is still largely the same gamemode that shipped with the base game back in 2012 and carries many of the problems that were prevalent even back then. GW1 managed to live so long in "maintenance mode" after new content stopped dropping in large part due to the thriving PvP community; that part of the game still remained dynamic even while the rest of the game became frozen in time. While I don't think things are so dire in GW2, it's definitely an important step in getting people engaged with the game again looking into the long-term.
...and while I hate to be the one banging this drum yet again, **please let us have the alliance system**. It's not a fix-all for WvW's problems, but MAN is it a strong first step.