I agree with several of those who are worried this is a waste of time and money, a fake "feature" that won't add to gameplay.
For one, AI interaction is already often inherently annoying, and without plans to fix that, this will just make things worse. I'm not for English voice acting either - I'd rather the AI just shut up entirely
I really don't need some leader coming to me in English, nor in some ancient Mesopotamian language and saying
"Would you care to trade maps, for 5 gold"
every single turn, which is about how often at least one AI makes requests.
If this is in the game, I hope there's an option to turn it off entirely; I probably would have it turned off after a couple of games if I'm playing civ V.
One related thing I would love, though, is the ability to conduct diplomacy without going into the diplomacy screen. No additional load time, no animating/voice acting/etc... for leaders, no changes in music, and so on. Ideally you would be able to set what conditions you want. So, say, if the Aztecs come knocking demanding you give them some technology or gold or something, you can just hit "ignore" and not even be forced into the diplo screen; maybe you'd be willing to listen to their declaration of war though. Simplify the system, make it customizable, and above all make the AI smarter, rather than wasting resources/processing time in game for "leaderhead graphics" and "voice acting" and all, especially if you can't turn such stuff off.