Sadly, we cannot know what those who die in their sleep actually dream of. All those that know are far beyond our ability to ask, and when we can, the question will no longer matter.
But I think that each dreamer's circumstances are... personal and different. Even those that dream of a similar place, a shared one, will not experience things the same. I have a friend here who dreams of the same world I do, but she is dreaming them far in advance, for instance. We are at different paces.