I saw that today in Steam on my Chromebook.
I thought it was a mistake, but after reading reddit, looks like its going to be real!
I'm extremely excited! Can't wait to try it in Linux natively
Of course my Guide will now be obsolete, but I'll leave it up anyways.
I bet its a similar deal as Witcher 2. If Borderlands 2 has high enough install numbers, then the Pre Sequel will get a Linux port.