If you believe the sleuthing done by several Reddit members, then some keen-eyed users may have figured out The Last Of Us 2's setting. According to this thread by Voldsby, who is notorious for finding these kinds of things in video games, it appears the locations are near downtown Seattle and around a section of the I-5. We have a snippet from the thread below, but we highly suggest checking it out!
While we can definitely assume that this "cult" is based in Seattle, since the proof is strong enough to confirm this, does this mean that Joel and Ellie will encounter these people during their next journey in Part II? Or do we encounter these people as the woman in the trailer or something entirely different?
I personally don't believe that the trailer takes place a few years into the outbreak or that the woman is Anna, mainly because the area surrounding the highway is too overgrown. The highway has basically become a forest with trees almost as tall as buildings, and since it takes at least 10-15 years for a tree to grow to that size (and even more for some), it pretty much rules out the possibility that this takes place only a few years after the outbreak.