Missions is not the ultimate goal of the church.  Worship is.  Missions exists because worship doesn't.  Worship is ultimate, not missions, because God is ultimate, not man.  When this age is over, and the countless millions of the redeemed fall on their faces before the throne of God, missions will be no more.  It is a temporary necessity.  But worship abides forever.

Worship, therefore, is the fuel and goal of missions.  It's the goal of missions because in missions we simply aim to bring the nations into the white-hot enjoyment of God's glory.  The goal of missions is the gladness of the peoples in the greatness of God.  "The Lord reigns, let the earth rejoice; let the many coastlands be glad!" (Ps. 97:1).  "Let the peoples praise you, O God; let all the peoples praise you!  Let the nations be glad and sing for joy!" (Ps. 67:3-4).

Piper, John.  Let the Nations be Glad.  Baker Books:  Grand Rapids.  2007.  17.