However, we must increasingly recognize that the language of “completion” can be comprehended only when missions is built on the foundation of Christendom, not on the foundation of the Trinity. Through the lens of the missio dei, we no longer isolate soteriology from pneumatology and eschatology. Therefore, even when every person has had an opportunity to hear the gospel, or even if a church is planted in every people group of the world, missions will not be over. Once missions is linked inseparably to the triune God, then the church recognizes that the ultimate goal of missions can be found only in the New Creation. This does not negate important goals such as planting a church in every people group in the world. However, it does mean that the church must always live in the tension of “unfinished business.” The mission of the church (missions) is to participate in the missio dei by continuing the mission of Jesus throughout the world until the end of history.
From Invitation to World Missions by Timothy Tennent p.100