Even now the kingdom exists and Jesus has ALL authority, Mtt 28:18. Even now He rules over all of the kings of the earth, Rev 1:5, and if they do not serve His purposes, He may shatter them, Psa 2:9; or He may destroy in their way, Psa 2:12.

Just the same, there are future aspects to the
kingdom which are yet unseen.

Mankind has yet to see the kingdom in its fulness. So near the end of his life, Paul says,

“And the Lord will deliver me from every evil work, and will preserve me for his heavenly kingdom; to whom be the glory forever and ever. Amen.”
2Tim 4:18 WEB

There is a future sense to this kingdom which is yet unseen, and Paul expects to be there. These things are to happen when Jesus comes again.

“20 and that he may send Christ Jesus, who was ordained for you before, 21 whom heaven must receive UNTIL the times of restoration of all things, which God spoke long ago by the mouth of his holy prophets.”
Acts 3:20-21 WEB

So there are times of restoration which are yet to come. It is also called “times of refreshing.

“Repent therefore, and turn again, that your sins may be blotted out, so that there may come times of refreshing from the presence of the Lord,”
Acts 3:19 WEB

When does this restoration, this renewal happen. At the Second Coming of Christ, as seen above in Acts 3:21.

Then this present universe will pass away.

“… ”the heavens will pass away with a great noise, and the elements will be dissolved with fervent heat, and the earth and the works that are in it will be burned up.”
2Pe 3:10 WEB

Then a new universe will come, a new universe where sin and death and entropy (things run down!) are no longer operating principles. So Peter notes,

“But, according to his promise, we look for new heavens and a new earth, in which dwells righteousness.”
2Pe 3:13 WEB

So also it says in Revelation that the apostle John says,

“I saw a new heaven and a new earth: for the first heaven and the first earth have passed away, and the sea is no more.”
Rev 21:1 WEB

“He who sits on the throne said, “Behold, I am making all things new.” He said, “Write, for these words of God are faithful and true.””
Rev 21:5 WEB

It is called “heaven,” or a new heavens and a new earth. It is called the heavenly kingdom. It will be an everlasting rule.

“Of the increase of his government and of peace there shall be no end …”
Isa 9:7 WEB

At that time, Jesus will say to
one Christian,

““‘Well done, you good servant! Because you were found faithful with very little, you shall have authority over ten cities.’”
Lk 19:17 WEB

And to another, “‘And you are to be over five cities.’” Lk 19:15. There will be cities there. This will be a real place. These things have not happened yet, but they will.

WEB is the World English Bible, a copyright free revision
of the original ASV American Standard Version 1901