Markus Bockmuehl helpfully points out that the alleged supersessionism of the early and middle chapters of Hebrews is seriously tempered by the later chapters, and particularly chapter 11, with its appeal to old covenant believers as the “great cloud of witnesses” who exemplify faith in God to the new covenant community.
“The undoubtedly supersessionist flavour of Heb. 8 and 9 is seriously misread of one takes it as the author’s general theological principle for the heritage of Israel and of the Old Testament. As the context of those chapters makes clear, the claim of obsolescence is in fact highly specific in its application, and concerns primarily the Old Covenant’s cultic apparatus of atonement…. The superiority of the New Covenant introduces not a new people of God so much as a newly energized worship of God – constituted around the definitive and permanently efficacious sacrifice. It is that difference in which the discontinuity of the covenants subsists, not in the identity of the people of God or even in their faith.”
“Abraham’s Faith in Hebrews 11,” The Epistle to the Hebrews and Christian Theology (Eerdmans, 2009), 367-368.