"I don't look old, HK, do I?"
I'm thinking back to when WoW was two and a half years old and I can't even imagine anyone calling it old back then. Then again, WoW's popularity was still rising rapidly at that point. So maybe our perception of a game's age has less to do with how long it has been out than with how popular it is. Consider EVE Online, a game that is over eleven years old by now but experienced a lot of pretty steady growth during that time. I for one don't see anyone dismissing EVE as old.
However these days, with people's tendency to jump on the bandwagon of every new launch and then abandoning the game a couple of months later, the road to being considered old and forgotten is a fairly short one. Not to mention that many new MMOs see a lot of pre-launch hype these days, meaning that by the time the game actually gets released, it can feel as if you've already been engaged with it for several months or even years.
So is SWTOR not popular enough anymore? The truth is, it's hard to say. Back when the hype surrounding the game was at its peak, Bioware loved to throw around metrics about how many subscribers they had and how long the average player was playing per day. Ever since the free-to-play transition however, talking about metrics seems to have become a bit of a taboo around Austin. It's already a surprise when they dare to release information such as "Vanguards win more than half of their arena matches". In EA's quarterly financial report, SWTOR gets lumped in with other games and you can't really tell how well it's doing beyond a vague notion that it seems to be making some money for EA. Individuals can share observations about how their server is bustling or a ghost town, but as the saying goes, anecdotes are not data. Personally I think that there is still a decent amount of interest in the game though. If nothing else I thought it was telling that, back when Massively suffered its staff cuts, the SWTOR column was one of the ones to be thrown out, but has now actually been brought back. They wouldn't have done that if there wasn't still a healthy amount of interest in the game.
In my opinion one or two years after launch is actually a great time to get into a new MMO. By that point, the launch issues that every MMO experiences have been ironed out, and the game's system requirements don't seem nearly as steep as they were on release. It's probably cheaper than it was at launch (if it's not free to play anyway) and may even have had an expansion or two, offering players a considerable amount of content to play through. At the same time it shouldn't yet suffer from the problems that some of the genuinely older MMOs experience, such as a lack of low-level characters to interact with or systems bloat that makes it hard for new players to come to grips with the game.
When do you consider an MMO (or a PC game in general) "old"?