JOEL - The phrase "Eternal Progression", means just what it says. Those who have obtained the highest level of the Celestial Kingdom will continue to progress in some fashion that we do not completely understand at this time. Those who obtain Eternal Life not only live forever but also live to the quality of life that God lives. We have been told that we will inherit "thrones, kingdoms, principalities, and powers," and dwell with God and Jesus Christ forever (D&C 76:54-70; 132:19-20).
Joseph Smith said, "But those who are married by the power and authority of the priesthood in this life, and continue without committing the sin against the Holy Ghost, will continue to increase and have children in the celestial glory" (TPJS, pp. 300-301).
Therefore one of the ways we progress in the Celestial Kingdom, called "eternal increase", is through having spirit children who will supposedly obtain bodies and live on an earth as we did and continue their own journey of progression.
We will never become the same as God, for He himself will be forever progressing in glory and we will always be subserviant to Him. However, we know that God's work, and the source of his glory, is bringing to pass "the immortality and eternal life" of his children (Moses 1:39). And If we are to follow in His path, we might therefore assume that our work and glory will be to bring to pass the immortality and eternal life of our own spirit children. We will progress in the sense of obtaining more glory as a result of the progression of our own spirit children.
As far as we know, we will not progress in the sense that there is a place to go even more glorious than the Celestial kingdom. We have been told that this earth in its "sanctified, immortal, and eternal state" will become a celestial sphere (D&C 88:19-20; 130:9) and will be our home throughout the eternities. One might ask if we will progress in the sense of gaining more knowledge and power. If in the eternal future we are able to become as God, then there must be a time when we reach His state of perfection, being all powerful and knowing all things.
Ideas have been advanced to explain how God might progress in knowledge and still be perfect and know all things, but there is just no way we could understand right now how that can happen.
In fact Elder Bruce R. McKonkie has stated, "It should be realized that God is not progressing in knowledge, truth, virtue, wisdom, or any of the attributes of godliness. He has already gained these things in their fullness. But he is progressing in the sense that his creations increase, his dominions expand, his spirit offspring multiply, and more kingdoms are added to his domains. (Doctrines of Salvation, vol. 1, pp. 5-10.)
No official Church teaching specifies all the ways in which God progresses in his exalted spheres. There may be other ways that we will be able to progress that have not been made known to us yet. One thing to consider is that all of this happens so far into the future that we don't really need to concern ourselves with all the details right now. It's best to concentrate on the here and now and measure our progression one day at a time.