The use of the word "heaven" or "heavens" many times was a metaphor for the kingdoms of men. Moses, speaking to the Israelite in the desert,
"Give ear, O ye heavens, and I will speak; and hear, O earth, the words of my mouth." (Deu. 32:1, KJV)
Moses was not calling God in heaven above. He was calling two different groups of the people - those that ruled, and those that were ruled - the Levitical priesthood, and the rest of the people. There was a distinction as the Levitical priesthood represented God and were to dispense His words to the people, therefore they were called "the heavens".
In speaking to Judah and Jerusalem, Isaiah said,
"Hear, O heavens, and give ear, O earth: for the Lord hath spoken, I have nourished and brought up children, and they have rebelled against me." (Isa. 1:2, KJV)
Again, Isaiah was not telling God to hear him. He was speaking to the people, two groups of people. The heavens was a metaphor in this use for the ruling authority in Judah and Jerusalem, which were at that time the king and his court, and the priesthood. By contrast, the rest of the people were the "earth" living under the rule of their "heavens" of the king and the priests.
Heaven began to be used for other nation's rulers and kingdoms as well. In discussing the manner of the destruction of Babylon, Isaiah told them,
"5 They come from a far country, from the end of heaven, even the Lord, and the weapons of his indignation, to destroy the whole land." (Isa. 13:5, KJV)
where "the end of heaven" was a metaphor for the borders of the lands of Babylon. The army was going to come upon Babylon from outside its borders - from the end of heaven.
The king of Babylon had authority and dominion over his lands, his territory. He ruled that nation and land just as God rules over all lands of the entire earth. The king of Babylon held dominion over a small part of the earth, and his kingdom was a type of "heaven".
So, in Col. 1:23, Paul stated he had preached the gospel to every creature under heaven. In context, in which country, territory or kingdom was Paul preaching? He went through the lands of Asia Minor, and Greece, and the isles of Greece. All of those lands were ruled in the first century AD by the ancient Roman empire. So who held dominion over that "heaven"? The ancient Roman empire.
"And it came to pass in those days, that there went out a decree from Caesar Augustus that all the world should be taxed." (Luke 2:1, KJV)
Just as Augustus only held authority to tax his kingdom, Luke 2:1 referred the Roman empire as "all the world", or "the whole world" which is used in the ISV. First audience perspective must be kept in mind.
The heaven of the Roman empire heard the gospel news by 62 AD when the letter to the Colossians was written. Then the "end" would come.
Too many assume that the "end" referred to the end of time, or the end of the entire natural physical world. But, that was not the end which was meant by the prophesy. The end was the end of the Mosaic animal sacrificial temple, which was the consummation of the ages (Dan. 9:27).
Jesus told the disciples in Matt. 24-25 that the temple in Jerusalem would be destroyed. That was the fulfillment of Dan. 12:5-13 for the "end of the days". And, Dan. 12:7 defined the end of the days.
"And I heard the man clothed in linen, which was upon the waters of the river, when he held up his right hand and his left hand unto heaven, and sware by him that liveth for ever that it shall be for a time, times, and an half; and when he shall have accomplished to scatter the power of the holy people, all these things shall be finished." (KJV)
The prophesy given to Daniel was stated in Dan. 9:24 to be about Daniel's people and Daniel's holy city. Daniel's people and Daniel's holy city were the Jews and Jerusalem respectively. They were not the Russians, the Chinese, the Americans, the French, or any other nation. They were the Jews, specifically of Judah.
The end of that prophesy was when the power of the holy people (the Jews) would be scattered. Other translations use the word shattered. It means completely broken. Their power was broken when that temple was destroyed in AD 70, and the disciples knew that any destruction of their temple was a judgment from God, a COMING OF THE LORD, and the end of their world as they knew it.
The prophesies never spoke of the end of time. The end was always about ending the animal sacrificial system which God hated (Isa. 1:11-17). The innocent animal was taking the place of the men and women who were the true sinners. Christ's sacrifice on the cross was the last blood sacrifice that God would ever require again for repentance and salvation. The old temple had to be removed in order for the spiritual kingdom to be fully established which it was in AD 70.
More is explained and offered at my blog, ShreddingTheVeil.org. Specifically, "It's Not The End of the World - Part X: And Then The End Shall Come" here, and "Signs of Revelation - Part I: The Time of His Coming" here.