X-Wing as a game should be viable for a number of years. Even when they slow down the release of content, it is still popular enough that there will be people playing it regularly. It can't last as long as other games because it isn't able to generate new content for itself, but the content that it does have is enough to last it a while yet.
Even then, I suspect that this game will continue to be played for some time like a certain fantasy grid iron game that hasn't died despite no longer being supported by the original company for well over a decade.