“Look at Nikon's history…. D100 (DX) was the small pro body companion to the D1H/D2H (DX). D200 (DX) was the small pro body companion to the D2Hs/D2Xs (DX). D300 (DX) was the small pro body companion to the D3 (Nikons first FX). D700 (FX) was the small pro body companion to the D3s/D3x (FX) D800 (FX) is the small pro body companion to the D4 (FX)”
I see Nikon’s history a bit different… D100/D1/D1H are all of the same generation. D200/D2Hs/D2Xs are all of the same generation D300/D700/D3/D3s/D3x are all of the same generation. D800/D4 are the current generation.
The D3 and D300 were released together. The D700 came out later but had the same sensor as the D3 putting it in the same generation as the D3 and D300. The fact that the D3s got a new sensor is kind of a fluke as an (s) upgrade is usually a smaller update. If you are going to separate the D3s as its own generation - then it stands alone with no companion bodies.
So, if history is an indication we should expect a small body DX camera for the D4 generation just like we had with the D3 generation.
Of course Nikons is not that easy to predict. There are several places where they have strayed from the past – for example there is no high speed (H) model for the D3 generation.