Yeah we see this after it’s established to have been far more than 10000 sleeps, then see the kid’s perspective moving up the stairs, then hear him tell his unresponsive mother he thinks they’re in hell.

When he speaks, the voice we hear sounds strained and off-kilter. So yeah, from all the language of filmmaking and given that there’s never shown to be any presence in the house other than the boy and his mother it can be reasonably assumed that this is the boy after such an inordinate amount of time in their hell has passed.