I think McKnight hits the nail on the head. Wright is not talking about doing away with Penal Substitution, rather, setting it in its proper context. There’s a tendency in us, younger theologians, to move away from Systematic Theology, onto Biblical Theology, that’s why we don’t see any fault in Wright’s methodology, and still accept Penal Substitution, and can’t understand the complains by Reformed theologians, and their fan boys, that we are on the wrong (in contradiction to them, being on the “Wright” side) of Penal Substitution.
What we are seeing here is not so much a clash of theology, as a clash of methodology. The Reformed critics of Wright do their theology of penal substitution systematically. Wright does his historically/narratively. Unfortunately, Wright does not appreciate Pierced for our Transgressions for what it is (a marvelous systematic look at the doctrine of penal substitution). But neither do Wright’s critics appreciate Wright’s work for what it is (a marvelous grounding of this doctrine in historical context).