John

I think this is one of those "already, but not yet" things.
We have Christ's righteousness imputed to us, but we must continue to grow in the grace and knowledge of our Lord Jesus Christ.
The context of 1 John 2:28 is being unashamed before Christ at His coming. We are not passively waiting for our Lord Jesus to come back; we are actively doing things like proclaiming the Gospel and trying to bring glory to God through obedience of the Word of God.

Tom