https://www.cnet.com/news/sony-a6400-touts-improved-autofocus-and-object-tracking/

It's slated to ship in February at $900 for the body, in a kit with a 16-50mm f3.5-5.6 lens for $1,000 or in a kit with the 18-135mm f3.5-5.6 lens for $1,300. 

The new hybrid autofocus system has the same 425 phase-detection points as the A6300, but bumps the contrast-detection areas from 169 to 425. That's important, because contrast AF is what the A6400 (like most other cameras) uses for subject tracking. In addition, Sony threw in some AI to help with object recognition, and now the company claims it handles real-time eye tracking and has improved object recogition and faster AF subject lock. Win-win-win. Animal eye tracking will come in a future firmware update.