Wanting to upgrade for indoor newborn and wedding photography. Currently have D7k.

I currently have a d5100 and a D7000. I love both of the cameras. However, when doing indoor photography for weddings or newborn photo shoots I would like to get better AF. Sometimes it hunts a little too much. Also it seems like in low light situations I get front or back focus a little more than I would like. And I would just like to have something that AF's faster in low light. I am thinking of upgrading to a D700 and selling my D7000. I am also debating on waiting and getting a D800. But I know the D700 has been out a long time and is a GREAT camera. And from what I can tell the D700 is easier to get great shots from it than a D800 because of the extra MP's in the D800. Any advice greatly appreciated.