Good thoughts, Nick. Thanks! 
I think I mainly agree with you, but I believe Iād emphasize the graduality of the process even more. Iāve begun to notice in the last ten or so years how everything on earth and in the heavens seems to exist in some sort of gradient, and I agree with GMac that the natural creation is a book for us, to teach us who God is. It is, insofar as uncorrupted, or so far as we can to some degree perceive what it might BE, uncorrupted, a portrait for us of our Father and of His manner of working in more distinctly spiritual dimensions. Regarding this gradient idea, an example I think of sometimes is our local white-tail and black-tail (mule) deer. I used to think of them as two separate species, but here in the conflux of the two, they arenāt really. There are white-tail and various mixes, and then mulies. Thereās a gradient between the two ā no firm dividing line as of pure whitetail --> 1/4:3/4 --> 1/2:1/2 --> 3/4:1/4 --> pure mulie.
To me, thinking of these āstepsā of justification, sanctification, glorification is artificial, and not the way we really see things in nature. I think probably these steps are intermingled. Justification (dikaiosune) is a complex word which, as far as I understand, has to do with being together in love and mutual respect with our brothers and sisters and our God or, as Jason has put it, āfair togetherness.ā Sanctification (hagiadzo) means to make holy, to purify and consecrate. This is maybe a thing with which we cooperate, but which we canāt really do effectively on our own ā maybe like treating a cavity in our own tooth ā (move this way, open your mouth a little more, donāt bite the dentist . . . next time donāt forget to brush and floss . . . .) I think these two can and typically do grow simultaneously. And as they grow, we also become more glorious ā we display the face of our Lord more and more clearly. It doesnāt seem to me that weāre meant to see this as three different and progressive stages, of which we must complete the one before we can enter into the next in the series. As we grow in the first ā as we learn to live together in love and kindness and fairness to one another and with our Lord, we naturally and at the same time become more and more unlike the corruption of the world and more separated out unto God, and as these are happening, well, āfrom glory to glory He transforms usā ā we begin more and more to shine with the glory that is His life and His beauty shining out from us.
Like you, I do think there has to be a ācrossing overā beyond which He becomes all in all and the natural world is renewed, the dead all raised, the corruptible puts on incorruption and all is at last one (as we now see that God is one). I wonder though, whether weāll ever cease to become more like Him. Heās infinite after all, and weāre not. So for us to be changed into His image seems to me likely to be a never-ending, ever more glorious quest. How can we ever fully attain to the fulness of Christ? This to me seems a wonderful thing, always to be exploring Him and His glory to higher heights and profounder depths. What a great adventure!
Anyway, this is my idea of āheavenā (in part). Just me musing. 