Since there is only one "imminent" appearance of the Lord and at that appearance the saints will be caught up to meet the Lord then those who received the Hebrew epistles were expecting to be caught up to meet the Lord Jesus in the air. And that is exactly what John is speaking about here:
"Beloved, now are we the children of God, and it doth not yet appear what we shall be: but we know that, when he shall appear, we shall be like him; for we shall see him as he is. And every man that hath this hope in him purifieth himself, even as he is pure" (1 Jn.3:2-3).
John refers to the things which will happen at the Lord Jesus' "appearance" as a "hope." That is exactly what Paul speaks of here:
"Looking for that blessed hope, and the glorious appearing of the great God and our Saviour Jesus Christ" (Titus 2:13).
When the Lord appears then the saints will put on glorious bodies just like the glorious body of the Lord Jesus and in the following verses Peter is speaking about that very thing:
"The elders which are among you I exhort, who am also an elder, and a witness of the sufferings of Christ, and also a partaker of the glory that shall be revealed...And when the chief Shepherd shall appear, ye shall receive a crown of glory that fadeth not away" (1 Pet.5:1,4).