They've been talking about going that direction for a little while now. There has been some talk about actresses that they want - Melissa McCarthy, Kristen Wigg, Sarah Silverman, and one other whom I can't remember off hand. However those are just early names thrown around, I don't think any of them have even been approached.
I hadn't heard that they wanted it to be a complete reboot though - last I heard they wanted to have the old team "pass the baton" to the new team.
I'm surprised to see allt he hate for it in the comments, all these "Do they think women will watch it?" Heck, I'm a guy, and I don't think the Ghostbusters franchise would be ruined by a female team. My dream team of female comedians for it is 1) Sarah Silverman 2) Alex Bornstein 3) Amy Schumer 4) Mindy Kaling, with Aubrey Plaza and Tina Fey as a backup.