It is not something that happens sometime in the future, long after our death, but something which we already are that we may come to realize right now.
One of the major themes in Disney's Frozen II is the journey into the unknown, which is a common element of the mystical journey into communion with the Divine.
This song is almost like a "First Vision" in itself, full of mystical allusions and symbols, suddenly realizing the Light, the Love, the One.
It seems the more we see outwardly, the less we see inwardly? Some thoughts on the nature of the veil.
The "new" union-covenant with God is found inward, not outward.