The already leaked Tamron 50-400mm f/4.5-6.3 Di III VC VXD lens for Nikon Z-mount is rumored to be officially announced tomorrow. Check for pre-order links at our sponsors:
The leaked details for the Nikon Z-mount version can be found here:
Details of the upcoming Tamron 50-400mm f/4.5-6.3 Di III VC VXD lens for Nikon Z-mount leaked online
The same lens already exists for Sony E-mount:
Tamron 50-400mm f/4.5-6.3 Di III VC VXD lens released, available for pre-order for $1,299
Via NikonRumors