The idea of getting two VIves so my wife and I could both play things together down the road has been briefly entertained but it's a bit too ridiculous for right now. Maybe I'll just keep the first gen Vive when the next one comes out.
Whats kind of neat is that the DK2 will probably still be useful for a while as a low end option. Many DK2 owners can repurpose their headsets for "player 2" hardware. Going forward, I could see OSVR being popular for that role, because it's a much cheaper headset than the high end ones.