The central message of this sermon is that God has given humanity a "upgrade" in terms of revelation and understanding through Jesus Christ, who is the ultimate expression of God's nature and identity. This upgrade means that there is no going back to the old covenant or previous forms of revelation, as Christ is the final and complete expression of God's character. The sermon emphasizes the superiority of Christ over the prophets, highlighting his role as creator, redeemer, and sustainer, and how he has made all things new through his sacrifice. The takeaway is that hearing from Christ directly is a significant improvement over hearing from prophets or intermediaries, as it provides a direct understanding of God's nature and character. This upgrade also implies a profound change in human relationships with God, as believers are no longer subject to the old covenant and its limitations, but rather have a direct relationship with the Son who has made atonement for sins.