The D610 release will most likely kill the market for used D600, which already was taking a hit for a while. In a month or two, you'll probably be able to find screaming deals on them, especially if you can find one without oil/debris issue or one that's had the shutter mechanism replaced (which is what Nikon started doing to D600 returned for oil/debris issue).
Also - holy poop, the used price on a 35L has come down significantly of late.