Built into the game i think it would create too many problems for the end user plus support. There are a few decent progs out there plus i think it built into steam i think, you just need to set it up. There is also teamspeak which works well.
I honestly hope not. In iRacing this is one of the first features I learned how to turn off. In racing games voice chat is used much more often for berating, yelling, and anger than it is for fun or helpfulness. All in all it really isn't worth the time and effort of implementation, particularly when there are so many 3rd party programs that already do just that in a much more controlled environment like Teamspeak, Ventrillo, Discord, etc.
The chat will be worked on: "SO: Absolutely. We have plans to add proper text chat, vote kick and vote next track. JFC: A chat box with ability to talk while on garage menu and scroll up to read what was said, that’s all I wish for." As for voice, like Jkck said, use teamspeak or mumble or whatever. We use mumble and it works great.