In a recent interview with Us Weekly, Milo Ventimiglia, who plays Jack on This Is Us, said the show is still "a ways off" from filming his character's death scene.
Viewers of the show know Jack isn't alive in the present day, as Rebecca is remarried and Kate has her father's ashes. However, we've yet to find out how Jack dies. It's sure to be a crushing episode, but with filming for Season 1 already wrapped, we won't have to worry about seeing it this season.
"I don't think it's scaleable—I really don't think it's scaleable," Ventimiglia said when asked how sad Jack's death will be for viewers. "It's one of those things that [series creator] Dan Fogelman [does where] you're making people fall in love with Jack and Rebecca and the relationship with these kids and everything, that I really feel people are going to be crushed when that moment comes."
Fans have come up with plenty of theories about how Jack dies, but we can't know for sure. At least we won't have to hold our breath watching this season's final two episodes!