What is the significance of Winston's dream in which a voice speaks to him about meeting in a place where there is no darkness?

The actual significance of this statement is not found out
until the third book.  However, once can make several speculations regarding O'Brien
saying this to Winston in his dream.  Winston, from the very beginning of the novel, has
an idea in his head that O'Brien is a sympathizer with the "Brotherhood", an underground
group, led by Goldstein, whose purpose is to overthrow Big Brother.  Winston, because of
this belief, feels some sort of connection to O'Brien.  I see two viable explanations
that Winston's character might be grappling with. First, the place where there is no
darkness could refer to a time when the "darkness" of the Big Brother regime has passed
and life can go back to the way it was before the revolution that occurred after World
War II.  Another possible explanation (a much less optimistic and dark one) could be
referring to them meeting in heaven once they are dead.  The "real" explanation,
however, is a surprise revealed toward the end of the novel.  I think, however, that the
saying is a source of inspiration to Winston, at least, initially. It’s a promise of the
end of Big Brother one way or the other in Winston’s eyes.