If I was mainly doing wildlife, I'd get a D7200 instead of going FX. You could have a wide angle on one and the Tamzooka on the other. I don't see what more the Fx format would bring you except maybe 1 stop extra light but at the loss of 1,5 crop factor...
This..Except now that the D400 may be coming into the picture, I would wait and see what happens with that. (If I was shooting mainly wildlife of course). I terribly miss my D7100 now for BIF shots since I bought the D750.