Primarily, I do wildlife. Probably 95% of the time, with the other 5% going to macro.
I do own the 1.4, 1.7 and the 2.0 TC, so I am good with many areas.
My prev. lenses were all DX, so I am wanting to maximize their use, while look at the FX repertoire.
I have the older 80-200, on which I stuck the 2.0 TC for a long time, until I got the 500mm. It is very heavy to tote around, but fills a great niche.
There have a lot of great photos show up on Nikonians with a D4, with various lenses. So part of outfitting it, is determining which glass is best. Having spent so much for the 500m, I hesitate to buy another pricey one. But if one like the 300 f/4 is not as good quality of glass as the 200-400, it might be prudent to save a bit more and get the latter.
So basically, the same old dilemma of quality vs. cost.
"Today is the tomorrow that yesterday you spent money like there was no"