Here's a bit more detail about that in-engine Stalker 2 trailer

In a post on the official Xbox blog, GSC Game World has given a bit of description to that in-engine teaser trailer from early January. Stalker 2's protagonist is Skif, whose eyes we see through in the teaser video. That's the character's Stalker name, remember, as Stalkers don't use their real names. (They are criminals, after all.) According to GSC's post, Skif's actions "will shape the new grand chapter in the history of the Zone."

Perhaps most satisfyingly for me, the trailer scene is...