And I do see hope as well in the ending.
I always have, too, though in a way I'm sure others would disagree with or find controversial. Whatever it is that we see through the trailer window, waving in the wind, just prairie grass or some kind of growing grain, it's green. It's alive. It's growing.
If the filmmakers had wanted to convey despair, they could just as easily have had something yellowed, dried-up, and dead visible through that window. But they don't. We see something alive.
And it's something waving in the wind. This might be the point for some comment about "Jack is the wind," or whatever, but I've never followed that thread of thought, so I'll stop here.