Making, Not Replacing
"He who was seated on the throne said, 'I am making everything new!' Then he said, 'Write this down, for these words are trustworthy and true.'"
— Revelation 21:5
Two details matter. The Greek word for new here is kainos, which means renewed in quality rather than brand new in kind. God is not throwing this world away and starting again. And the verb is present tense: I am making, not I will make. John was writing to churches under pressure who needed to know the work had already started.