The newest 747s are 2003/2004 models. Thats only 4 years younger than the A380s.
The 767s had D checks and full cabin reconfigurations then shortly after retired.
Like wise the 747s had D checks then retired.
Joyce has said publicly that the sunrise type will or could replace the A380 from 2023. Going on the 747 retirement add 4 years to the A380 and that’s exactly 2023 in line with Alan’s Comments.
Just as the 787 has and will replace the 747.