Nikon will officially release the firmware updates for Nikon Z6 & Z7 on May 16th. This new firmware will add Eye-detection AF for Z6 & Z7. According to NR, this firmware will also improve low light focus capability for Z6 & Z7.
Nikon Europe said on Youtube the previous announced firmware updates for Nikon Z6 & Z7 will be released on May 16th, 2019. This new firmware update will add Eye-detection AF, CFexpress support and Raw video over HDMI to the Z6 and Z7, and also AF and AE improvements for Z6 & Z7.