Is the gospel being preached to all nations a sign of the end?
Yes. Scripture directly ties the preaching of the gospel of the kingdom to all nations to the coming of the end, teaching that the end will not arrive until every nation has heard it.
Jesus himself gives the clearest word on this in Matthew 24:14, "And this gospel of the kingdom shall be preached in all the world for a witness unto all nations; and then shall the end come." This is not presented as a side note but as a condition that must be fulfilled. The end of this age will not come until the gospel of the kingdom has gone out into every nation. There is only one kingdom and one gospel of that kingdom, so this preaching to the nations stands as a genuine marker on the prophetic timeline, not simply background noise to other events.
Mark's gospel repeats this same truth in the middle of Jesus' teaching on persecution and the last days: "And the gospel must first be published among all nations" (Mark 13:10). This places the worldwide preaching of the gospel right alongside wars, earthquakes, famines, and the betrayal of believers by their own families as part of the unfolding pattern that leads to the end. It is listed as something that must happen first, before the final events fully arrive.
Some have taught that there are actually two separate gospels, the gospel of Jesus Christ preached now for salvation, and a different "gospel of the kingdom" preached only after the church is removed, announcing the coming Millennial Kingdom to those left behind. But the teaching here is firm that there is but one kingdom and one gospel concerning it, the very gospel that is being preached now and that must reach every nation before the end comes.
Because this reaching of the nations is treated as a sign, the sense of urgency is strong. The timeline appointed for the preaching of the gospel is described as winding down to a close, and the revelation of the antichrist is said to be closer than many think. The gospel will reach all nations regardless of any individual's participation, because God will accomplish His purpose, but each believer's reward and place in that harvest depends on whether they gave, went, sent, or prayed toward that end while there was still time.
The scriptures
And this gospel of the kingdom shall be preached in all the world for a witness unto all nations; and then shall the end come.
But take heed to yourselves: for they shall deliver you up to councils; and in the synagogues ye shall be beaten: and ye shall be brought before rulers and kings for my sake, for a testimony against them. And the gospel must first be published among all nations. But when they shall lead you, and deliver you up, take no thought beforehand what ye shall speak, neither do ye premeditate: but whatsoever shall be given you in that hour, that speak ye: for it is not ye that speak, but the Holy Ghost. Now the brother shall betray the brother to death, and the father the son; and children shall rise up against their parents, and shall cause them to be put to death. And ye shall be hated of all men for my name’s sake: but he that shall endure unto the end, the same shall be saved.
Now we beseech you, brethren, by the coming of our Lord Jesus Christ, and by our gathering together unto him, That ye be not soon shaken in mind, or be troubled, neither by spirit, nor by word, nor by letter as from us, as that the day of Christ is at hand. Let no man deceive you by any means: for that day shall not come, except there come a falling away first, and that man of sin be revealed, the son of perdition; Who opposeth and exalteth himself above all that is called God, or that is worshipped; so that he as God sitteth in the temple of God, shewing himself that he is God. Remember ye not, that, when I was yet with you, I told you these things? And now ye know what withholdeth that he might be revealed in his time. For the mystery of iniquity doth already work: only he who now letteth will let, until he be taken out of the way. And then shall that Wicked be revealed, whom the Lord shall consume with the spirit of his mouth, and shall destroy with the brightness of his coming: Even him, whose coming is after the working of Satan with all power and signs and lying wonders,
From the books
This answer is drawn from these passages in the Mary Banks Faith Library.