The end of Westworld season 3 saw William, a.k.a. The Man In Black, meet his host counterpart (with a dramatic end), so what will William do as a host in season 4? Jonathan Nolan and Lisa Joy's science-fiction series is based on Michael Crichton's 1973 movie, about a Western-themed park where robots gradually gain consciousness and start to revolt against the people who controlled them for so long. The series premiered on HBO in 2016, and it was a huge hit worldwide. Westworld's season 3 left viewers with many questions and a lot of timelines waiting to be explored in the next season.
The Man In Black (Ed Harris/Jimmy Simpson) is a Westworld veteran who has been visiting the park since its very beginnings, three decades ago. He invested in the park side by side with his brother-in-law Logan (Ben Barnes), but William would also behave in the most inhumane ways towards the park's hosts. Later, he started working on The Forge, a project which recorded the behavior of (not the hosts, but the) guests, with a goal for immortality. The first prototype for this project was James Delos (Peter Mullan) himself, the founder of Westworld, but his mind couldn't accept his body, so the project failed, with William laughing it off and leaving Delos to lose his mind in a room. However, Westworld season 2 showed William as a host in a similar scenario with host Delos.
While Westworld season 2's post-credits scene was set in a distant future yet unexplored by the series, the season 3 post-credits scene laid the ground for that future. It showed William, who had spent most of season 3 in a hallucinatory state in a therapy clinic, arrive at a Delos facility, only to find a host version of himself, programmed by the Charlotte Hale (Tessa Thomspon) version of Dolores (Evan Rachel Wood) to kill him. Now, Charlotte had host William by her side, as well as a host army in the making, and the real Man In Black was most likely dead. Did that mean William would collaborate with Charlotte in her plan to take over society? Charlotte told the real William that it was really easy to replicate him, indicating that the host was entirely loyal to William's mind. That could also mean that host William wouldn't stay by her side for too long, as William had a history of disobedience. It seems likely that, although created to fit Dolores' plan, host William will find his own destructive path throughout Westworld season 4.
The real Man In Black emerged from his psychiatric treatment promising to "save the world" as the executioner of every host outside the Sublime. If host William copied his real counterpart truthfully, it might not be a surprise that he will be on a quest to kill everyone – except this time, it would be humans he wants to purge the world of. Westworld season 3's both post-credits scenes pointed towards season 4 focusing on multiple timelines, with Bernard (Jeffrey Wright) waking up from the Sublime covered in dust in a now-empty motel room. The lack of a riot outside the motel might indicate a humans vs. hosts war that has left the world in a post-apocalyptic state in the future timeline. It is very likely that host William has a big part to play in this.
There is another detail in the season 3 finale worth mentioning. When host William slit William's throat, the latter was seen grabbing his wound and falling to the floor, but the camera moved away from him before he could give his last breath. Considering that the cutting-edge technology used to repair hosts' wounds works on humans, too (as seen on Caleb in the last season), many fans expect the real William to come back for Westworld season 4, too. A clash between two Williams who have unleashed their darkest sides creates endless possibilities for the new season.