This is planned: http://trac.wildfiregames.com/wiki/Audio_Voice_List
However, it's hard to achieve. Since ancient civs didn't own very good audio recording tools. We'll always need to guess the pronunciation.
For some civs, we don't even have many written sources.
Next to actually learning the pronunciation, the one doing the recording should also have access to some sort of semi-professional audio studio, and should have a good vioce. And on top of that, since not all soldiers should have the same voice (and females should have a different voice for sure), we need many recordings from different people.
This has been requested many times. But it would complicate the pathfinder a lot.
And you might know that we already have issues with the pathfinder (lag, inconsistencies, ...).
So don't expect this feature in the next few years, even if it's one we dream of too.
Too complicated for the main game IMO. Also too much micro. Maybe mods that focus more on single units could implement this.
Remember that we're volunteers. Writing and producing music takes a lot of time. We're happy that Omri does such a good job at writing music.
He manages to make a few new music pieces per year. There currently are already 32 pieces recorded.