The principle that parables speak about the mysteries of the Kingdom is only mentioned in the first mention of parables in Scripture. We find it, besides Matthew 13:11, only in the parallel texts in Mark 4:11 and Luke 8:10. After that, it is not repeated, although we do find other indications of this. For example, in the parable of the pounds. There we read:
Luke 19
11 And when he heard these things, he added a parable, because he was near Jerusalem, and they thought that the kingdom of God would immediately be revealed.
public vs hidden
Because the disciples thought that the kingdom of God was about to be revealed, the Lord tells them a parable, the parable of the pounds, which we also find described in the remainder of Luke 19.
This parable, like the other parables, does not speak about the revealing of the Kingdom, but about the fact that the Kingdom would be hidden and about the period that the Lord would be absent (Luke 19:12).
hearing not hearing
Parables were told by the Lord Jesus so that the people would ‘hear but not understand’ (Matt. 13:13). We find spiritual truths and illustrations hidden in parables about a hidden Kingdom.
The expectation for Israel was about a revealed Kingdom. They did not want the sent Messiah, Jesus Christ, to become King over them (Luke 19:12). Therefore the message was hidden from them and the expectation they had, the revealed Kingdom, was taken away from them (Matt. 13:12). The Kingdom became a hidden Kingdom.
sharing in His Kingship
We are part of that hidden Kingdom. But in a special way. Our life is hidden together with Christ in God (Col. 3:3). When He shall appear, that is, be revealed, we shall appear with Him in glory (Col. 3:4)! Christ shall reign as King and subdue all things (1 Cor. 15:28). He shall subdue all enemies (1 Cor. 15:25-26).
Head and Body
Christ is the Head of the ecclesia, which is His body (Eph. 1:22-23; Col. 1:12) and we as His ecclesia shall share in His function and position. We shall receive heaven and earth together with Him as our allotment (Eph. 1:10-11). He is not our King, but our Head and as His body, we shall share with Him in His Kingship.
Colossians 1
13 He has delivered us from the power of darkness and conveyed us into the kingdom of His dear Son.