As my study of the Church Fathers grows deeper, I have come to wonder about the propriety of theological discourse. Can (should!) anything new be said? In one sense no, in another sense yes.
The point of academic theology is twofold: to pass along what has gone before (the Tradition) and to use that to speak afresh to our times and places. So, if we are just in the business of the first aspect, then, no, theology cannot say anything new. It is bounded by Jesus Christ's person and work. We speak of Him and no other. However, language changes, situations change, challenges come up, and we must speak of Him somewhat differently at times (the homoousias controversy seems to speak to this -- how do we confess what the Church confesses and safeguard that from Arian misunderstanding?): however the bulwark by which our theological language is judged is not the culture or the history or the place, but Jesus Christ Himself. Even in our re-expression we must avoid theological novelty.
Does this mean, though, that theology is complete? By no means.
The subject of theology, the One whom we long to know (and I don't mean knowledge in a purely "rational" sense here), is, by nature, infinite. So our knowing of Him progresses truly, but slowly as we are drawn deeper into His Life (the Holy Spirit) in His Body (the Church). Theology itself, then, is the infinite study of the Infinite One. We will never (thank God!) be able to say, "Well, now we know all there is to know." Nor will we be able to fully express it. All the other subjects, because they are being joined to Christ (Eph. 1:10ff.) are the same way: we may see (for example) an atom in various equations, or models, or super-collider experiments, but we still cannot comprehend -- have exhaustive knowledge of -- an atom. Nor shall we ever. We have true knowledge, but only partial. We look into a mirror darkly.
It is interesting, in this regard, that both Sts. John and Paul, at different points, basically say that someday, eschatologically, we will fully participate in this infinity, "knowing even as we are known."