In the end days, God will reveal more things to us which are now sealed. But God, through His Spirit, is also revealing some of them to us even today that which were previously sealed before the coming of the Christ. All that we learn from the New Testament and through the gift of the Holy Spirit was earlier sealed and people did not understand clearly. God will unseal more things to us in His perfect time.
‘In the last days, God says, I will pour out My Spirit on all people; your sons and daughters will prophesy, your young men will see visions, your old men will dream dreams. Acts 2:17
So when the time for the events in the Revelations occur, then everything will be unsealed to God's children who live in that time as it will be needed for them.