Tamron still doesn’t know if they will develop mirrorless lenses for Nikon Z-mount – the company is currently researching the new mount and exploring their options.
Because of the major differences between the three full-frame mirrorless mounts (Sony E, Canon R and Nikon Z), Tamron cannot just adapt the current Sony mirrorless lenses to Z-mount.
It takes Tamon approximately 1.5 years for Tamron to develop a new lens – the earliest we can expect to see new Tamron Z mirrorless lenses would be in early 2020.
Tamron thinks it is important for them to offer lenses for Nikon Z and Canon R mounts.
Source: Phototrend, via PhotoRumors