The New Testament has its own distinctive tradition-historical development with its own peculiar dynamic and its wide range of diversity. It is not simply a continuation of traditional trajectories from the Old Testament. Indeed a serious confusion of categories results when the canonical unity of the two testaments represented by the Christian Bible is translated into merely historical categories as if the Old Testament flowed by inexorable laws into the New Testament. Rather the New Testament has its discrete historical context, its traditions were treasured by different tradents, and its central force stems from another direction than that of the Old Testament. Thus the New Testament is not a midrash on the Old, nor is it simply the last chapter of a story. Even the term 'Heilsgeschichte' calls for careful nuancing since it represents a theological judgement respecting continuity and is not simply a claim for empirical historical judgement (Biblical Theology, 212).
Update: The blog Theological Ramblings of an Anglican Ordinand provides us with some useful N.T. Wright quotes showing us the nuance in Wright's approach:
Worldviews may be studied in terms of four features: characteristic stories, fundamental symbols; habitual praxis; and a set of questions and answers.