Here's the thing. You've entered a sweepstakes and the prize is "any current Nikon DSLR." Which one do you take?
We have a couple of variations on how to play the game.
First up, DX only.
At the end of 2013 your choices were D3200, D5300, D7100, and D300s. I think it's easy enough to eliminate the D3200 (all the other options provide you something the D3200 doesn't, at no penalty). The D5300 has the swivel LCD, the D7100 has more features, and the D300s has the most features, best build quality, but can't match the others in image quality.
The choice for me is easy: take the D7100. The only things you give up is the swivel LCD of the D5300, the buffer/buttons/build of the D300s. You get the best image quality and close to the best feature set, though.
Will the answer change in 2014? Probably, though only if a D7200 or a D300s replacement appear.
Next, let's try FX.
At the end of 2013 your choices were D3x, D4, Df, D610, D800, and D800E. That's a much tougher choice, because those cameras are all over the place. There's also the clear option of taking the most expensive camera, selling it, and buying a less expensive one ;~). But I'm going to assume that you're stuck with the one you choose.
You can't pick the D3x because the D800 is better in image quality, and the build quality difference just doesn't justify picking the D3x, even if you love vertical grips (you can always add one to the D800).
You can't pick the D610 because the D800 is better in image quality, features, and to a small degree, build.
If you're always shooting at ISO 3200 and above and/or you need very high frame rates for what you shoot (e.g. sports), then you clearly pick the D4.
The only reason you pick the Df is probably because you like dials. (It's not better in image quality than the D800; it's not better in frame rate, features and build of the D4.) I write that a bit sarcastically, but the only other thing I could come up with is that it's a bit smaller and lighter than the others, or you are shooting above ISO 3200 an awful lot and don't care about frame rate or focus system. Most people aren't going to pick that way, I think.
Will the answer change in 2014? Well, if you were choosing a D4 in 2013 you'd choose a D4s in 2014 ;~). Other than that, I'm not sure. It doesn't seem like a year when we'd get new iterations of the D800 or Df. Perhaps a D4x might appear, and that might change the equation.
Now it might seem silly to play this game, but it does have a function. One of the questions I get asked every day is "should I buy an X or wait?" Okay, play the game. What's your answer for 2013? Now how likely is it that 2014 will change your answer? Right now it's only the D7100, D300s, and D3x users that have a high probability to have their answer change in the coming year, I think. If you picked something else, then the answer is most likely "don't wait."
So how long should you wait? New DSLRs will come in February and August, I think, with the much slimmer possibility of one late year arrival, as well.
Stay tuned for The Nikon DSLR Sweepstakes Game, 2014, coming to you in January 2015.