I have been preoccupied with 2 Corinthians 3:18 today. Tonight I came across two comments, from Phillip E. Hughes and also John Calvin, who both stress the ongoing transformation until our bodies are glorified. Hughes notes,
And to contemplate Him who is the Father’s image is progressively to be transformed into that image. The effect of continuous beholding is that we are continuously being transformed “into that image”, that is, into the likeness of Christ-and increasingly so: “from glory to glory” (The Second Epistle to the Corinthians. NICNT, 117-118).
And Calvin notes a similar emphasis on continual transformation when he writes,
He points out, however, at the same time, both the strength of the revelation, and our daily progress. For he has employed such a similitude to denote three things: first, That we have no occasion to fear obscurity, when we approach the gospel, for God there clearly discovers to us His face; secondly, That it is not befitting, that it should be a dead contemplation, but that we should be transformed by means of it into the image of God; and, thirdly, that the one and the other are not accomplished in us in one moment, but we must be constantly making progress both in the knowledge of God, and in conformity to His image, for this is the meaning of the expression — from glory to glory (2 Corinthans, 187).