It was great to have an actual hands-on testing on the Sony A9 yesterday. The continuous AF tracking speed is unbelievable fast and the awesome part was "how the camera know which one i decided to focus on?" It did very well in this field (of course, it was build to the sport purpose) *advice: Better prepare a fast and bigger capacity SD card for that. You can simply hit 2k to 3k direct output Jpeg Fine in a short period of time. For sure you will never miss any moment.
High ISO is not a big problem even your output render in Jpeg format. Dynamic range is great when come to indoor or low light situation, no worries for the details even at ISO 6400 Jpeg. Excellent details, unless you zoom in more than 100% or 200% to see the very fine render of noises.
Camera: Sony A9
Focal Length: FE 24-70mm F2.8 GM @ 70mm