Unfortunately we still don't know. Dan has not released that information yet. And until today this was still a fart in the pants rumor. We knew Dan wanted a female member, but no one knew he wanted that female member to be the leader of the group.
Dan recently gave an interview to The Guardian, in which he talks a little about his future plans for the Ghostbusters franchise and what kind of weapons we can expect to see in the third film. Dan states "There'll be a whole new generation that has to be trained and a leader that you'll all love when you meet her," says Aykroyd. "There'll be lots of cadets, boys and girls who'll be learning how to use the neuron splitter and the inter-planet interceptor - new tools to enable them to slip from dimension to dimension."
I guess this news replaces a popular male comedian as the leader, I thought Steve Carol was going to land the role of the new lead for the team or Vince Vaughn. Don't get me wrong I like hot females as much as the next guy, I just think it is the wrong move. Remember guys don't fix what's not broke.