Let me hypothetically pose a hypothetical situation to you. One day, you find yourself in a ~~parallel dimension~~! It is just like normal, an average tuesday, chatting on Facebook (like usual) and talking with all your friends remotely. You call up one person and invite them over; it's just like every other time you've done so. Everything's the same. You talk, you hear, on both ends of every conversation. However, your friend (lets call him Moist), after talking and playing some AoC for a while, has the brilliant idea of going to see the Evil League of Evil, the elite team of super-villains. You travel all the way over to their secret headquarters - signing in using the secret password - and listen in on their fabulous and devious schemes. All is as it should be.
But soon things start to go wrong. After you leave the base, you decide to go to the frozen yogurt market. All sorts of frozen yogurt vendors from across the galaxy gather there to hawk their sales. But once you arrive, the world is in dead silence. Well, not complete silence, because there are the sounds of birds chirping in the background and some distant music (and ancient times) playing alongside. But nobody speaks. Whenever you walk up to a vendor, they shout a greeting to you, then hand you a slip of paper with a conversation on it - in the best case situation, you get to give a response (on paper, of course). Not that you have a choice what the response is, or whether you get to give it or not, but a response nonetheless.
Now, more astute metaphoricists will have noted, Hey! That's just like the current state of all MMORPS! Egads! Gadzooks! Conker! And you would be right. Walking down a back alley in Stormwind has exactly the same sounds as walking through the market district - it's all the same. Bioware is, you might say, the King of getting this.... nearly right. Playing through Denerim's market district has vendors hawking their wares, reactive responses from your party members, and fully-voiced dialog. MMO's can pick this up, and SW:TOR will probably be the first of many fully voiced MMOs to come. Well, nearly fully voiced. Because there has been one piece of the situation always missing.
That would be the player. Even if you are given 5 options to speak, you are only given 5 options - whether you can predict a new outcome or not, see the trap before it's sprung, have a counter-argument the developers never thought of, or generically make a pretty funny joke, it doesn't matter. It never matters. You only have the words, phrases, sentences, given to you at your disposal. Perhaps they will give the character a voice of their own at some point (though this runs the risk of further distancing the player from the character's dialog). This is how RPGs have always been, right? This is how they have been since their inception. WRONG.
RPGs began with the pen-and-paper - the In the Labyrinths, the DragonQuests, the DNDs. In these, NPCs did not exist (at least not how we think of them currently). Every character had a human brain behind them, from a goblin to a wolf to an orc to a housecat. Each was fully reactive, and the depth of the character was based on the person behind it. With MMOs, nowadays, NPC 'intellect' can be increased to a degree of nigh-impossibility, in the gameplay of the game - but they remain woefully ignorant in terms of Speech.
How do we solve this? There are a few options, and I'll list them in terms of time:
1) Add a ventrilo-style chat, in game, in place of a text-based system for /say speech. Have it diminish in terms of distance, how speech does now. Communities will shun those who yell stupidly - if not, ignore features and the like will follow just as text-based speech has forever.
2) Add a decent STT (Speech To Text) system into these games. This is mainly heightened by option #3, however it does allow for a fair bit of interesting potential - first, it is faster than typing, and allows for Text just as fast as you would receive voice commands (great for raiding or PvP or other quick decisions). Also, it frees up hands for doing whatever - fishing, grinding for Shadowmourne, dancing - while you can 'type' in guild chat with speech. As I said, though, mainly heightened by #3.
3) Add a decent TTS (Text To Speech) system into these games. Add accents, variants, sliders and more to increase customization - this will allow both players to role-play easier and more effectively, as well as allowing dynamic NPC speech without needing thousands upon thousands of Voice Actors (as in SW:TOR). Would make voicing in games nigh-infinitely easier. Also, sadly, by far the most difficult of the bunch. Possible, but difficult.
Modern AI will handle the rest - the anger, the inflection, the character behind the words. All it takes is for these to be built, and perhaps the Bazaar won't feel like a graveyard (no matter the number of people in it) any more.