Don't believe the memerless IDF when it comes to BIF and sports. Mirrorless AF has still yet to best the algorithms in use by DSLRs, although they've seemed to have caught up in speed. Also, EVFs a shit, even the a6300 at 120 fps.
The 7D2's a mini 1DX, but don't expect too much improvement sensor wise from the 7D. 7D2 came out too early for the new crop of Canon sensors, which are much improved. If you're capable of getting good shots from the 7D, the 7D2 will continue doing so but with vastly more sophisticated metering and autofocus.
The D7200 compares more to the 70D and 80D in terms of tier. The sensor is (still) class leading (can't do a 4-5 stop push on your Canon), the autofocus is yet another evolution of the D3's highly capable CAM3500 (less cross types than Canon's 65 pt though, only center 15 are cross, rest are line), and Nikon's subject tracking is unmatched by anybody. Frame rates are positively slow by Canon standards (5 RAW, 6 JPEG/crop RAW, 7 crop JPEG).
The D500 is the same tier as the 7D2, but without the benefit of nearly $1000 of price drop (original price vs grey market today). The 7D2 is ridiculously cheap for its capability level, honestly. The D500 is vastly more capable however. The AF is more sophisticated, the frame rates are right up there, the sensor is highly capable.
If you've got the lenses already, might as well get a grey market 7D2 for what, $1200? Before Trump shuts that down.