In Matthew 10:23, Christ tells the disciples that they will not finish going through the cities of Israel until the Son of Man comes. It is these last couple words, "the Son of Man comes" that I think leads the Preterist to assume that Jesus is talking about the second coming. Hence, it is argued that the gospel is preached to the entire world according to the New Testament before A.D. 70, the end is to come after it is preached to the whole world, and certainly the cities of Israel are included in that. Hence, since the disciples themselves are the ones doing the preaching, and they preach the gospel to the whole world, again, including Israel, before A.D. 70, this must mean that the disciples will be alive when Christ returns.
There are a couple of issues with this interpretation however. In the context, Christ is sending the disciples out to the cities of Israel during His earthly ministry. Verses 10:5-10 makes this clear.
Jesus sent out these twelve, instructing them as follows: “Do not go to Gentile regions and do not enter any Samaritan town. Go instead to the lost sheep of the house of Israel. As you go, preach this message: ‘The kingdom of heaven is near!’ Heal the sick, raise the dead, cleanse lepers, cast out demons. Freely you received, freely give. Do not take gold, silver, or copper in your belts, no bag for the journey, or an extra tunic, or sandals or staff, for the worker deserves his provisions.
Notice that the disciples are told not to go to the Gentiles, which is the opposite of what Christ will command them to do at the end of the book in the Great Commission (Matt 28:16-20). This tells us that this mission is a more localized one and one that comes before the other in Christ's earthly ministry.
Christ also tells them not to bring provisions with them. This is also the opposite of what He will command them later when they go out to the nations after He leaves them (Luke 22:35-38). Again, this indicates that the mission in Matthew 10 is not the same one as the Great Commission later.
There is also a problem in harmonizing what is said here with the idea that this refers to the global mission that ends with Christ's return. Jesus states that the disciples will not finish going through the cities of Israel until the Son of Man comes. He does not say that they will finish before He comes. He states that it is not until the moment He comes that they will finish. His coming marks their completion of the mission and having gone through all the cities. It is the point of their finishing.
The world-wide mission is said to be completed long before Christ comes. Preterists are fond of quoting Paul who states that the gospel has been proclaimed in all creation under heaven (Col 1:23), that the voice of those who preach the gospel has gone out to the ends of the world (Rom 10:18 quoting Psalm 19:4), that it is bearing fruit and growing in all the world (Col 1:6).
But Christ says that they will not finish going through the cities of Israel until He comes. What this indicates is that the Son of Man coming is throwing off the Preterist interpretation. They are reading an eschatological coming into the text when Christ is simply referring to Himself as the Son of Man who will come to them at the point when their temporary mission during His ministry is completed.
And, indeed, the preaching itinerary of both Christ and the disciples indicate that they would have covered all of Israel within His earthly ministry.
One might argue that the lost tribes of Israel were scattered among the nations, and hence, Christ is referring to the whole world, but the problem with this is that the text clearly states that Christ tells them NOT to go into any of the cities of the nations/Gentiles. They are not even to go into the towns of the Samaritans. So it is clear that this is referring to the northern towns of Israel, where the northern tribes were once located and still had members of those tribes in them. Again, the disciples would have completed this task within a short time frame. Northern Israel is not that big.
So His coming has to do with His coming to them at the completion of their mission, not some eschatological coming in A.D. 70 or otherwise.
Now, what of the argument concerning the end taking place once the gospel is preached to the whole world, as in Matthew 24:14? I think there is a twofold fulfillment of this in terms of the micro-macro argument. The end for Israel in the destruction of the temple in A.D. 70 occurs after the gospel has been proclaimed to the whole Roman world. Matthew 24 is about the destruction of Jerusalem in A.D. 70, so this would make sense. So in a microcosmic manner, it is fulfilled in the same way that the destruction of Jerusalem is a microcosm of the larger destruction of the world to come.
However, it should be noted that it is not clear whether Christ is referring to the world in the same way that Paul is. Christ uses the word oikomene, which refers more the literal creation of the world, the entirety of the created order, the whole inhabited earth. Paul merely uses kosmos or ktisis in his hyperbole, but does not seem to be quoting Christ or alluding to the prediction in Matthew 24.
I would also argue that Paul is speaking in hyperbole, not literally. In fact, all must conclude this as the gospel had not, in fact, been proclaimed to all the world as a literal fulfillment. It had in terms of a representative fulfillment, a micro fulfillment of what would come, etc. The idea that Paul did not know of the world outside of Rome, of course, is complete nonsense. Everyone was well aware that a larger world existed outside of the Roman Empire. So Paul's declarations here are meant to be hyperbolic, but Christ's prediction seems to be literal.
Furthermore, Paul displays that this message being heard by all the nations from his own personal proclamation, as though he is the one personally to have told the entire world the gospel, which is another indicator that he is using hyperbole here, and is not literally saying that every nation has heard the gospel from his own lips. The idea instead is that the gospel has gone out, not only to Israel, but to the entire world, all of creation in a sense, and has spread beyond the borders of Israel to the furthest boundaries of the Western Empire and to much of the East, covering the expanse of the entire Roman world (cf. 1 Clement 5:5-6). Hence, one could argue that the entire world had the gospel preached to it in a hyperbolic manner, since Rome was not the entire world, but made up the entire Empire that ruled Paul's world. The gospel had not yet gone to China or to the tribes in the African bush, or to the Barbarian tribes outside of Rome, etc. all of which Paul would have known to exist. But he uses hyperbole to show just how extensive the preaching of the gospel, i.e., his own work, truly was.
He likely states this as a counter to the claims of Judaizers that the gospel is for those who become Jewish. In any case, his claim uses hyperbole to counter the idea that it is for the Jew and not also for the Gentile (Hence, the two books in which he makes these statements are Romans and Colossians, two books dealing with heretical Jewish teaching).
But it is also clear that the gospel was meant to go out to the entire world, all of creation, not only in the hyperbolic sense in which Paul is using it, but literally. This is only being fulfilled recently in our own time.
Either way, since Christ's prediction is literal and Paul's claim is hyperbolic, and because there are very clear microcosmic and macrocosmic fulfillments of this prediction (no one would argue that the gospel is actually proclaimed to the entire known world of the First Century audience), one can say that this both had a fulfillment in the First Century but also needed to be fulfilled in the future if it was to be fulfilled literally.
In conclusion, Matthew 23:10 is not talking about some eschatological fulfillment, but merely stating that the disciples will not finish their work of going through the northern towns of Israel before Christ comes to them to end that temporal ministry.