Ripeness
Our world's union with God lies at the End of a ripening process. It will not be a going back, a mere return to our starting-point, but a going forward.
The end of the world is not only a termination but also a goal. The fulfillment beyond that termination is also a continuation.
The end cannot come until human society is ripe, life's possibilities duly realised.
Union with God is not an absorption, an amorphous melting into the divine being. And it is not a like an erotic bond of unilateral or mutual obsession, though its early stages may resemble that, as with a young child whose mother is his world and who will always love her but needs to grow out of such absorption. Union with God is not detached from our present developmental task; it fulfills that task, not by finishing it and "putting it away", but by taking it to a new level.
The life to come is the next stage for humanity, "more but not less" than life as we know it, beyond current possibilities. In the present life, performing our task involves aspiration and effort, and in relation to this the future life is restful, but this does not imply inaction or stagnation. Maybe we should think of it as a retirement that frees us for better things.
All the good that has ever been experienced, by humans or any other selves, is only a foretaste. The Hebrew prophets anticipated a future golden age, and the earliest Christian writers insist that the body is a permanent feature of human life, that fulfillment will be not escape from the body but enhancement of the body (1st Corinthians 15:35-44). But we can form no adequate picture of that life.
"Jerusalem the golden, with milk and honey blest,
beneath thy contemplation sink heart and voice, oppressed.
I know not, oh! I know not what joys await us there,
what radiancy of glory, what bliss beyhond compare."
John Mason Neale, The Whole World Lies in Evil (1851).