They should NOT be made perfect (complete) without
us - a "better thing"
for us(Hebrews 11:40)
The promise was to be received in resurrection, the perfected
(completed) and "better" state (Hebrews 12:22-23), as confirmed by the Lord Jesus Christ (Luke 20:37-38 cf. Exodus 3:6)
There wiil be those in Israel at His Second Coming
to earth who will experience "a better thing", i.e. NOT dying (Revelation 12:1-5) and will receive a resurrection
body (Revelation 14:1-5 cp. Revelation 7:1-4) together with those who
are raised from the dead at that time (John 3:1-10 cf. Ezekiel 37:1-14)
There wiil be those in the Body of Christ at His Secret
Coming in the air who will experience "a better thing", i.e. NOT dying (I Corinthians 15:51) and will receive a resurrection
body (I Corinthians 15:52-53) together with those who
are raised from the dead at that time (I Thessalonians 4:15-17)