Bruce Charlton has a valuable essay up on theosis and the difference between Eden and Exaltation.

Offers of paradise are merely us as we are dwelling in perfect conditions; but in real Heaven it is us as we have become, dwelling in perfect conditions: the gap between us as we are and us as we have become is called theosis – it is the process through which men become more like God.

Salvation is qualitative (yes-no) while Theosis is quantitative (how much?).

Read the whole thing.