None of the cameras except the D4 are really targeted to pros but surely many will avail themselves of the IQ advantages by the D800 and D600. Working around a minor change in habit is surely also not going to stop them, nor all the Canon shooters who are working pros with 5D series who have 1/200 sync but also several stops less in DR.
I think this sort of "deal breaker" talk that happens wherever a new camera comes out, will disappear shortly after those who figure out new methods to take advantage of the increased capabilities start describing their techniques. I am going to venture a guess that the D600 will be very popular for pros wishing to step up their product and wanting a faster return on investment. Most of my shooing is with flash or strobe and 1/200 would be of little concern to me because there are so many ways of adopting. I am not likely to get a D600 but if I had not gotten the D800 before, I sure would have considered the D600. I do like the AF and that alone is probably worth the $900 price difference to me. The -1ev AF capability of the D600 just might surprise a lot of people how much better the FX version of the 4800 is over the DX version.