"Behold, I give unto you power, that whatsoever ye shall seal on earth shall be sealed in heaven; and whatsoever ye shall loose on earth shall be loosed in heaven; and thus shall ye have power among this people."
What the gospel asks us is to live on earth in ways that we want sealed in heaven, and through the Atonement to loose ourselves on earth from what should not be sealed to us in heaven. Exaltation is not an entirely separate state of being: it is a sanctification, purification, and endless continuation of what the deepest and most basic gospel principles allow us to build on earth.
Have prophets with sealing power been waiting for thousands of years to seal up the whole earth? No, I think they've understood that their role is to prepare and perhaps to seal pieces. The Messiah, when he returns, will be responsible for sealing everything, and people in the millennium will help him.