Two-and-a-half years ago, I wrote a post about the level 1 to 20 zone of Age of Conan, called Tortage. That post ended with a look into the future, about Star Wars: The Old Republic: "And would a game which had Tortage-like storytelling throughout be a smash hit? Bioware is apparently betting on the latter with Star Wars the Old Republic. Here's hoping." I have a theory about that, which I mentioned in my subjective opinion post about SWTOR, but apparently it is difficult to explain.
My general model of MMORPGs is that they consist of an endlessly repeating part, like combat, or you could call it more generally "gameplay", and a non-repeating part, which you could call "content". The gameplay of Tortage in Age of Conan is exactly the same as the gameplay in the rest of the game. But the content part of the two halves is very different: In Tortage you play through an engaging "destiny" quest line with great story-telling, afterwards the storytelling gets much thinner and less engaging. People noticed that break, and because Tortage was the only part of the game accessible during beta, players felt like they had fallen for a bait and switch confidence trick. They didn't care that the gameplay of the second part was identical to that of Tortage, they cared for the destiny quest and the storytelling, and felt cheated. Thus Age of Conan managed to lose two thirds of its subscribers after the first month, and is generally considered to be less than successful.
Fast forward to 2011 and if you look ONLY at the gameplay, Star Wars: The Old Republic plays exactly like World of Warcraft, with minor modifications. But most of the people playing SWTOR don't care, because what is important to them is the other part of the game, the content part. On the content side SWTOR beats WoW hands down. SWTOR has fully voiced dialogue cut-scenes for every quest, WoW has 511 characters of text to read. Yes, the two very different ways to tell the story, to tell the quests, lead to the same sort of "kill 10 foozles" gameplay. But people don't care all that much about gameplay, they care mostly about content. So the reception of SWTOR is generally positive, because players feel they are getting something very different from World of Warcraft, because even if gameplay is very similar, content is very different.
But with content being its greatest strength, content is also SWTOR's greatest weakness. Because as I said in my definition, content is the non-repeating half of the game. The gameplay part can be repeated very, very often; some of us killed a million mobs in World of Warcraft. The content part loses dramatically on repetition. Playing the Esseles flashpoint the first time is great, playing it the fifth time you forget about the dialogues and cutscenes and just concentrate on the gameplay.
Thus it is very likely that players will have a Tortage moment once they reach the level cap at level 50. There will still be a game after reaching the level cap, but it will be very different from the leveling game. It will be strong on gameplay, and weak on storytelling and content. You'll still log into a game of the same name, but that Star Wars: The Old Republic you'll be playing at level 50 will *feel* very different from the game you are playing now. You won't meet new, interesting characters and have interesting dialogues several times per play session. Instead you'll skip through the cutscenes and dialogues of the equivalents of dungeons, raids, and daily quests, because you have seen them many times before. The content has basically ended, and only the gameplay remains. And that might be a crippling blow to a game whose strength is the content, not the gameplay.