The question asked in Is 53:8 implies that someone will declare the generation of Jesus.  Isaiah doesn’t ask “if” someone will declare his generation.  And he doesn’t ask who “will” declare, as if the Lord is trying to find someone to declare his generation.  The Lord asks who “shall” in the sense of who are the people who are going to make this declaration.

Who shall declare his generation?

Those who have believed “our” report, Is 53:1.  This is a report from God.  This is not some contrived story or man-made fairy tale.  You are reading a report, a detailed account of a prophecy.

We have the word of God and we believe the report.  We are declaring something that God said and that we believe.  We have God’s words on it.

Those who have been healed by his stripes, Is 53:4-5.  Jesus bore our griefs and carried our sorrows.  He was wounded for our transgressions and bruised for our iniquities.  The chastisement of our peace was upon him.

We have a testimony of what Jesus has done for us.  We know firsthand that he did all these things for us.  We can describe the peace we have with God now, Rom 5:1.

Those who are his generation, Is 53:8.  Ps 22:30-31 “A seed shall serve him; it shall be accounted to the Lord for a generation.

They shall come, and shall declare his righteousness unto a people that shall be born, that he hath done this”.

We are the people that are born (born again).  We are accounted to the Lord for a generation.  The most common propagation of the gospel is from the mouth of a saint to to the ear of a sinner.

Conclusion: We are the ones who have believed his report, who have been healed by his stripes, and who are his generation.  We are the ones God will use to declare his generation.  If you haven’t been declaring his righteousness and generation, ask yourself why not.  And then deal with the reason and start telling others about him.  Will you declare his generation?