Do you not think three cameras is overkill? Unless you plan on linking them all wirelessly and trigger them that way two would suffice wouldn't it?
Reach is always good, so I would keep the 1D Mark IV and 1D X and sell the rest and buy new glass.
I like Mt Spokane Photography's idea of the new 200-400 lens.
How did you end up with so many cameras anyway?
I guess as time went on, I replaced all my old cameras with a new one. Had a 7D and 5D2, and got a 5D3 in place of those two. Then I stopped actually replacing them. Kept the 1Ds3 when I did that. However I did a few weddings and got another 5D3 because I was using that heavily and the convenience of two helped. The 1D4 I got in May to pick up the end of the track season. Oh and you can see how it went. Should have sold, much like I did my 7D and 5D2, as I went along.
I don't think 3 is overkill. I take two to every event. Sometimes the 3rd has a greater strength at one thing than another. So it could be A/B, A/C, or B/C, depending on what I'm doing. In THIS case though, sports is going to be it. I always carry two bodies to every event. But I'm only doing sports, then yeah, why have 3? I guess I'm not thrilled with the 1D4's IQ compared to the 5D3 or 1DX, but it certainly has that extra reach. In track the 400mm lens I have becomes 520. That's tough to beat, especially at low ISO.