The Great Commission and the Already/Not Yet

As far as I can tell, until the last few hundred years, the Church was unanimous in considering the Great Commission to have been fulfilled by the apostles in the first century. Currently, the Church appears to be unanimous in considering the Great Commission to still be awaiting fulfillment. Which is it? Were our fathers in the faith wrong, or are we wrong? Or are both positions both correct at the same time?
As has been noted by many people, the New Testament, is replete with statements that reflect the fact that many things have now been fulfilled in part in Christ's life, death, and resurrection and will be completely fulfilled in Christ's return. One example is that Satan was truly defeated by Jesus on the cross (the already). Yet he is the lord of this world, and he will be defeated fully when Christ returns (the not yet).
This concept also applies to the Great Commission. The Great Commission was given to the apostles. As Paul says in Colossians 1:6 (the gospel "has come to you, as indeed in the whole world it is bearing fruit and growing - as it also does among you, since the day you heard it and understood the grace of God in truth") and 1:23 ("not shifting from the hope of the gospel that you heard, which has been proclaimed in all creation under heaven"), the gospel had been proclaimed in the whole earth. Probably all of the Jewish communities were reached with the gospel by the end of the first century. The gospel had gone to the entire world with the apostles.
Additionally, the gospel has not yet gone to the entire world. The apostles presumably never went to the Americas or to Australia. It is unclear how far south they got in Africa, or how far east they went, or if the got to Britain. Clearly, not every tongue, tribe, people and nation were reached by the apostles, not have been yet. This will not be completed until Christ's return.
This is a relatively simple example of the already / not-yet theme in the New Testament, but it appears to be disregarded today. We should always been wise and gracious to faithful interpreters of the Bible. Perhaps we can both be right, and hence be a bit wrong at the same time.