Ironically the reverse of how it started. Originally they were faces without voices, now they'd be voices without faces. Personally, I think the time is decades off. Yes, we're talking 20-50 years.
I've explained to people that when they try to computer generate a living creature, (For example: The L.A. Times had a trailer in local cinemas showing a computer generated Basset Hound), that something in my brain just won't buy it. I have yet to be fooled.
Happily, an article has come out supporting my reasons. Quite simply, when animated figures don't look entirely human. Take Shrek for example, the characters are likable. Even the evil ones. But if you pass too close to human, (such as many of the newest video games), the figures become disquieting and a bit spooky. See examples by Brian Carpenter here and here.
There is some mystery of 'life' or that spark that animators just can't reproduce. The mind is programmed to detect those little inconsistencies that make something look 'not quite right'
I will admit, the person that figures out this miraculous, "Xeno's last step" is gonna be rich. On the downside, I take solace for now that they can't fool me into believing someone fake is someone real.