Deep Silver said that the game would be release alongside Windows on May 20th, 2016.

http://archive.is/kxaAf

After Liam from GamingOnLinux noticed that the store page on Steam only listed Windows he asked them on Twitter what gives and they said that Linux is still in develpment.

http://archive.is/Rs74s

Then, in April, Dambuster Studios said that day-1 release isn't happening.

http://archive.is/MZKXk

In October and November we saw activity on SteamDB with regards to a Linux depot and with more change logs, as reported by GamingOnLinux.

http://archive.is/bhHhD
http://archive.is/PO0U3

The latest update to the han_di_testing branch is currently 2 months old. Going off that, I will wait 4 more months to see if there is any activity or word from the devs/publishers.