2 posts in 1 year, I'm on a role!
Seriously though the game will last for as long as the server is kept open. I would be along the same lines as a lot of people here though. When I go online a lot of my old mates don't play anymore, or if they do it's few and far between. That and I was never much good with the rope except for my awesome Shadows!
There is no real element of achievement anymore apart from running leagues such as TUS, so when you finish a game it's like yay but no ranking points etc... Even in the games I play today I look at the ranking element of it.
What needs to be done to keep the game alive is an update at the start of Wormnet (And I admit I don't know I haven't been online for a while) That gives a link to the TUS website to promote new players to come to the website to learn what the community is about.
As was said Team 17 could decide one morning that they are going to be awesome and create a game based on WA with a new interface, weapons, schemes etc, but not messing up the mechanics of the game.
Alternatively what could happen and as an opportunity for someone out there who is into creating games etc. Would potentially be to go to KickStarter, make a campaign for a new game based off Worms Armageddon as a Spiritual successor. Instead of Worms it could be called Slugs (If you get my drift)
I am thinking Mighty No. 9 and the Nostalgia for that is immense as it relates to MegaMan.
Overall from thinking myself the community would be dead 10 years ago, to see it still going in 2015, I honestly think the Community is what will keep the game alive ultimately. The only problem is with a game like this at this age, it's very easy to get into the "what we had, or this is how it works" rather than looking to innovate, even on a website as awesome as TUS there are things that could be done, such as a dedicated chat for game challenges and a link directly into the hosting of the game rather than going through Wormnet.
Alas that's my rant! Long winded and less about the point then the original question, but that's me