In early modern missions, Carey and many of his contemporaries seemed to think that they were ushering in the Millennial kingdom in some sense. It’s interested that their optimism may have been partially misfounded, or misdirected; we are not commanded to Christianize all nations, but simply to preach, as the following from Chrysostom shows:
For the signs too are now complete, which announce that day. For “this Gospel of the Kingdoms,” saith He, “shall be preached in all the world for a witness unto all nations; and then shall the end come.” Attend with care to what is said. He said not, “when it hath been believed by all men,” but “when it hath been preached to all.” For this cause he also said, “for a witness to the nations,” to show, that He doth not wait for all men to believe, and then for Him to come. Since the phrase, “for a witness,” hath this meaning, “for accusation,” “for reproof,” “for condemnation of them that have not believed.”
So the goal of missions is not a Millennial kingdom; the goal of missions is that all may hear. May the offer of Christ’s grace go forth.
(Source: John Chrysostom, Homily X on Matthew. Phillip Schaff’s Nicene and Post Nicene Church Fathers.)