Then the end will come Matthew 24:14

"And this good news of the kingdom will be preached in all the world as a witness to all the nations, and then the end will come." Matthew 24:14

This end that Jesus spoke about, is the end of the age, and his coming. He said this as part of his answer to the disciple's questions, "What will be the sign of your coming, and of the end of the age?" Whether the disciples knew it or not, they had asked two questions in one, after they had asked Jesus about when it would be that, "Not one stone [of the temple buildings] will be left standing upon another. Every one will be thrown down." That's three questions all together. The temple was torn down in 70 AD, fullfilling that part of Jesus' decree.
But, what of the other two questions? They are interrelated. Verse 14 tells us of one certain thing, among others, that will happen before "the end" will come. 'The good news of the king's dominion will be preached in all the world, as a witness to all the nations' first, so the end can come. Many have assumed that the preaching of the salvation message is 'the good news of the kingdom.' It is part of it.
When Jesus returns, according to Revelation 19:16, "And he has on his robe and on his thigh a name written: KING OF KINGS AND LORD OF LORDS." Most of Jesus followers already recognize him as their King and their Lord. Then, if he is king at his return, what is the good news of the kingdom that must be preached as a witness to all the nations before his return? It is that there is an actual dominion in place, on the earth, now, even before he returns.
Suppose that this is not a contested point. How is the good news of his dominion to be known? His dominion is not known merely by words preached. Many will hear and scoff, not believing. Others would be simply unconvinced, except for Jesus' stipulation, "as a witness to all the nations."
While it is true that preaching can also refer to witnessing, there was much more than this that Jesus meant. He was not saying, the good news of his dominion will be 'preached as a sermon.' He did not mean it will be 'taught as a teaching.' Some versions of the Bible say the news will be preached "as a testimony."
The interesting aspect of 'a witness,' or 'a testimony' as meant in this verse, is like that of a witness in a courtroom, saying, "this is what I saw," or, "this is what happened to me."
The fact that Jesus' real dominion is in place on earth, before his return, will be seen, and known, or atested to, or experienced, and known. It will no longer be a 'matter of opinion.' It will be known. It will make the evening news. It will fill up the 24 hour-a-day news channels. Many who know Jesus and believe John 14:12 will do what Jesus did, "and greater things than these, because I go to the Father."