In 2012, Stephen J. Wellum co-authored Kingdom Through Covenant: A Biblical-Theological Understanding of the Covenants along with Peter Gentry. It was received well, though not without making a few people uncomfortable from both covenant and dispensational camps. The work was a critique of both systems (with regard to weaknesses perceived by Gentry and Wellum), but also intended to provide a constructive way forward via biblical theology. Here is a 5 minute YouTube video of Gentry and Wellum discussing Kingdom Through Covenant.
In the same vein, Wellum is now releasing Progressive Covenantalism: Charting a Way Between Dispensational and Covenant Theologies (B&H Academic).  Preorder on Amazon here.

On a different note (more a systematic theology genre than a biblical theology genre) Wellum is releasing God the Son Incarnate: The Doctrine of Christ (Crossway). This is his contribution in the Foundations of Evangelical Theology series (a great series!). Preorder on Amazon here.