Here's another option to consider...
Since your interest in the D4 / D4S is due to FPS... what about a Nikon 1 AW1 instead? With it, you can get an FT-1 lens mount adapter and use all of your existing SLR lenses on the Nikon 1. The AW1's crop factor then gives you 2.7X more reach for the wildlife & BIF shots without the additional weight of the D4 + super tele lens, especially since you can then use a much shorter FL lens. The 1 AW1 has much faster frame rate than even the D4S (15 fps vs. 11), and you still have 14mp.
Then, buy the D810.
You have the best of both worlds: the D810's extreme resolution in a full frame sensor AND the AW1's super fast frame rate in a reasonably high resolution sensor that gives you the advantage of 2.7X crop factor for wildlife, in a much lighter, handier package... AND getting all the above while still saving $2K over the price of a single D4! You could use that $2K toward another very good lens.
Yes, the AW1 doesn't have anywhere near the construction integrity/ build quality of the D4. The D4 will also handle high ISO much better. However, you can use the D810 for the bulk of your shooting where you don't need extreme frame rate. It will provide the pro build quality and the excellent high ISO performance. You should still be able to get decent low light performance with the AW1 and a fast lens without having to boost ISO to ridiculous levels. As for the AW1's lack of "pro-level" build quality, if it fails, you've saved enough money to buy 2 extra bodies. Keeping weight and bulk down is a huge advantage for wildlife photography, especially if you hike into remote locations.
As for IQ, I've seen some incredible images with great dynamic range out of the Nikon 1 cameras.
