In my opinion, unless there is an influx of new people from another location, WA will slowly die. Look at it this way: The composition of wormnet at the beginning, back in 1999, was mostly north american/brazil/uk/france/spain/germany. You could look at the list of people in the lobby and it would be tons of USA, canada, UK. Now the number of people from those countries is relatively small. USA is possibly the largest group of gamers (pure speculation) and are represented with a tiny fraction of wormnet overall. Speaking from my countries perspective, about 90-95% of the USA pros no longer play or are on extended leave.
I left for many years after 2003, and returned in 2009 for a very short time. Prior to this, I had never ever seen a russian flag on wormnet to my recollection, maybe one or two at the very most. By 2009, there was a absolutely huge contingent of russians, as well as other eastern european countries represented. Now, it appears the russian invasion has tapered off quite a bit.
Now, if you are following me here, a very clear pattern emerges as to the game being widely distributed and played in different countries that otherwise didn't play the game before. You would imagine for a new base to enter in now would take:
1. A monumental rise in popularity based on a powerful gamer with a huge base playing the game continually (think pewdiepie), if you don't know who this is, go to youtube and check out how many subscribers he has.
2. The game being distributed widely in a market that it otherwise hadn't before, possibly japan or china, but it seems that don't necessarily take to western games not named starcraft or LoL. I'd say it's unlikely at this point as even korean worms was never really that popular.
3. A move by team17 to solidify its user base around the classic worms games in the form of actually contracting CS and deadwood in a meaningful way that makes it worth their while to dedicate time (they have 0 interest, as the financial incentive isn't there for them).
4. A new spiritual successor to WA that brings all of us over, because they finally put out a product that combined the facets that we all love and put out a cohesive product that pulls us in (insanely unlikely at this point, in fact it seems to be going in the opposite direction).
Those are the only four factors I can actually foresee turning the tide, and none of them are really remotely plausible, but I hope that any of these things could happen.