Note, this is just an idea.
First, I like what games are doing with voiceovers, and it'd be cool if they upped that to getting rid of all text chat.
How, you ask?
Well, you can have the NPCs speak, thats been proven, and it's not too difficult. Improvements need to be made, but its getting there.
In regards to the players, what'd be cool is if they had some type of modulator that made what you said come out the way your character would say it.
I.e. If you are a Male Troll, what you say into your headset is modulated to sound like a Male Troll. If you are a female barbarian, it'd be modulated to sound like a female barbarian.
This would definitely add to the level of immersion, as well as helping some people eliminate the need for 900 numers