
Not really a confirmation, but this is what Tamron had to say in a recent interview on their plans to develop mirrorless lenses for Nikon Z mount (pretty much the same response they gave a month ago):

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.