As of 08/15/19, the Game Pass for PC version of Wasteland 2: Director's Cut is available again.
FAQ for customers:
Q: Does this affect anything other than the Microsoft Store on Windows?
A: No, this was specific to the PC version on the Microsoft Store on Windows only, which also impacted the availability of the title to Xbox Game Pass subscribers through the Xbox PC app, as they share the same Microsoft Store game builds. This did not impact the Xbox One version of the game or any other platforms.
Q: I downloaded the game before it was removed and was not having any issues, how can I continue to play?
A: You can continue to launch the game directly from the place you’ve installed it on your hard drive, but be aware that your save games will not be compatible with the version uploaded 08/15/19. Your save games will not be able to be continued in the future, so please plan accordingly.