The writers of the entire Bible from Genesis to Revelation had no training in astronomy or astrophysics. Neither did they know about “red giant stars”. That does not change any prophecy about the resurrection, matters of faith, or current science.

What the Bible does say is that the Lord God will make a new heaven and a new earth as a forever dwelling for all the faithful. Since God made our existing sun and solar system and the entire universe in six days, Almighty God has the capacity to make anything go away, dissolve the universe, and design a world fit for eternity at the speed of divine thought.

Secondly, the light that will illuminate heaven will be the divine light from the very glory of Jesus Christ in his divine state. There will not be a need for the sun or the solar system in the new earth and new heavens [all the stellar universe]. Jesus has been creating places for all believers now for at least two thousand years nearly. I cannot imagine the detail and particulars Jesus has in mind. So I am not worried about our Sun going to Red Giant status.

Jesus did promise to return on the Last Day of human history, resurrect all the dead both righteous and the wicked, change the living at the time of His return in the blink of an eye, judge every person from all of human history fairly, separate [actually throw them] the wicked into a lake of fire forever, and then celebrate with all the faithful in our new eternal home!

The universe only appears to be billions of years old because of the current speed of light. Based on Genesis 1, originally—. light could have had unlimited light speed. This would account for God saying,” let there be light”. Then when God separated light from darkness, He changed the speed of light to the current speed. This secondary change then made the universe seem much older.

Gen 1: 1 says that in the beginning God created space [universe, Hebrew word used was heaven] and matter [Hebrew word used was earth]. Therefore, I would not ascribe any limitation to Almighty God.

But I would note that God foretells literally melting this earth with fire in the book of Peter as a form of judgement. He destroyed the earth once with water in the flood. He promised not to repeat that action. The next time, He will use fire. Perhaps God will cause the Sun to go into supernova mode at that time. Who knows.

Those who are among the faithful will be with Jesus in that New Earth and New Heaven in Revelation.