And this good news of the kingdom will be preached throughout the whole inhabited earth as a testimony to all the nations, and then the end will come. - Matthew 24:14
I keep running into the thought expressed by some that the preaching work that Jesus speaks about at Matthew 24:14 is some sort of future preaching work.  I would be interested to know the basis for that idea.
Here are my thoughts:
At Matthew 28:19,20 Jesus gives the grand commission -
"Go there and make disciples of all nations ... teaching them to obey everything that I have commanded you."Â Â So there is a preaching work that begins just after Jesus' ascension.
Does this preaching work differ from the preaching work spoken about at Matthew 24:14? Â
I don't think so because the message is the same.  It is the message of "the Kingdom" and it is for all nations.  During his own ministry Jesus was preparing his twelve apostles (sent ones, missionaries) in order to preach this message.  When Jesus sent them out he gave them the "good news" message which was,
"The kingdom of heaven has come near" (Matthew 10:7)  This message than was the "good news of the kingdom".  Later Jesus would select 70 other disciples and send them out with the same message;
"The kingdom of God has come near you" (Luke 10:9) Now what about the message of that Jesus commissions just before his ascending to Heaven?  It too is a message regarding the Kingdom; specifically, Jesus' enthronement as King. Before they had gone out with the message that the Kingdom has drawn near and now the thrilling news is the Kingdom has become a reality. Jesus says,
"All authority in heaven and on earth has been give to me" (Matthew 28:18)Â Â
So to review:
- Jesus sends the twelve apostles preaching the "good news of the Kingdom" to Israel.
- Jesus sends the 70 out preaching the good news of the Kingdom to Israel.
- Jesus commissions his apostles and disciples to preach the good news of the kingdom to the nations.
With this in mind Matthew 24:14 seems to be the fulfillment of what Jesus has been preparing his disciples to do - that is to preach the kingdom message to Israel and all nations.  Jesus is here prophesying that they would successfully fulfill his commission to take the "good news of the Kingdom to all the nations" before the end would come.  Matthew 24:14 seems more like the culmination of the work that had started when Jesus was on earth and then got kicked off in a big way with the Christian congregation.
After Jesus ascension to Heaven the Good News of Jesus' kingship was preached to Judea and Galilee, then to Samaria and the Jewish Diaspora. The good news was carried by Paul to many parts of the Gentile world.  As we approach the time of the end of the Jewish system (70AD) the good news was preached to all parts of the Roman empire, possibly even coming so far as Britannia. There is evidence also that the message was taken even beyond to places like India and China.  Now in our day the good news has gone out to all parts of the Globe.
Are we today having a share in the disciple making work and promoting the "good news of the Kingdom" and of its risen King, Christ Jesus?  It would be a shame if we missed out on Jesus' commission while awaiting some sort of future preaching work. Â
"How are they to call on one they have not believed in? And how are they to believe in one they have not heard of? And how are they to hear without someone preaching to them?  And how are they to preach unless they are sent? As it is written, “How timely is the arrival of those who proclaim the good news.†- Romans 10:14,15