Matthew 24:14 has already been fulfilled according to these quotes.
See: w95 9/1 pp. 17-18 par. 17 Christian Witnesses for Divine Sovereignty
(Matthew 24:14; Mark 13:10) Has this prophecy been fulfilled? Indeed, it has.
Credit goes to Blondie:
*** w00 10/15 p. 11 par. 7 God’s Kingdom—Earth’s New Rulership ***Surely God’s Kingdom is the very best news for all who love what is right. That is why, as part of the sign that we now live in "the last days" of this wicked system, Jesus foretold: "This good news of the kingdom will be preached in all the inhabited earth for a witness to all the nations; and then the end will come." (2 Timothy 3:1-5; Matthew 24:14) That prophecy is being fulfilled now, as about six million Jehovah’s Witnesses in 234 lands devote more than a billion hours a year telling others about God’s Kingdom.
*** w97 8/15 p. 14 par. 11 Living for Today or for an Eternal Future? ***There is also Jesus’ prediction that "this good news of the kingdom will be preached in all the inhabited earth for a witness to all the nations; and then the end will come." (Matthew 24:14) Today, Jehovah’s Witnesses carry out their work in 233 lands, island groups, and territories. True, untouched territories still exist, and perhaps in Jehovah’s due time, a door of opportunity will open. (1 Corinthians 16:9) Still, Jesus’ words recorded at Matthew 10:23 are sobering: "You will by no means complete the circuit of the cities of Israel until the Son of man arrives." While the good news will surely be announced throughout the earth, we will not in person reach all parts of the earth with the Kingdom message before Jesus "arrives" as Executioner.
11. (a) To what extent has Matthew 24:14 been fulfilled? (b) What do Jesus’ words recorded at Matthew 10:23 indicate?
*** w95 9/1 pp. 17-18 par. 17 Christian Witnesses for Divine Sovereignty ***Still, that first-century preaching work was merely a foretaste of what would be accomplished during the last days. Looking forward especially to our time, Jesus said: "This good news of the kingdom will be preached in all the inhabited earth for a witness to all the nations; and then the end will come." (Matthew 24:14; Mark 13:10) Has this prophecy been fulfilled? Indeed, it has. From a small start in 1919, the preaching of the good news has now been extended to more than 230 countries. The witness is heard in the frozen North and in the steaming tropics. Large continents are covered, and remote islands are sought out so that their inhabitants can receive a witness. Even in the midst of great upheaval, such as the war in Bosnia and Herzegovina, the good news continues to be preached. As in the first century, the witness is bearing fruit "in all the world." The good news is openly announced "in all creation that is under heaven." The result? First, the remaining ones of the Israel of God have been gathered "out of every tribe and tongue and people and nation." Second, the millions of the "great crowd" began to be brought in from "all nations and tribes and peoples and tongues." (Revelation 5:9; 7:9) Matthew 24:14 continues to be fulfilled in a large way.
*** kl (Knowledge) chap. 11 These Are the Last Days! ***14. How could you prove that Matthew 24:14 is being fulfilled in our day?
This
goodnewsofthekingdomwillbepreachedinalltheinhabitedearth." (Matthew 24:14) Jesus foretold that the good news of the Kingdom would be preached earth wide, for a witness to all the nations. With divine help and blessing, millions of Jehovah’s Witnesses are devoting billions of hours to this preaching and disciple-making work. (Matthew 28:19, 20) Yes, the Witnesses realize that they would be bloodguilty if they did not declare the good news. (Ezekiel 3:18, 19) But they are delighted that each year thousands gratefully respond to the Kingdom message and take their stand as true Christians, that is, as Witnesses of Jehovah. It is an inestimable privilege to serve Jehovah and thus spread the knowledge of God. And after this good news is preached in all the inhabited earth, the end of this wicked system will come.