Jesus sent the Apostles to the world as His Apostles and witnesses to teach us all whatsoever and gather all who will hear His voice into ONE Flock. We must keep up with the commission.
And many nations shall come, and say, Come, and let us go up to the mountain of the LORD, and to the house of the God of Jacob; and he will teach us of his ways, and we will walk in his paths: for the law shall go forth of Zion, and the word of the LORD from Jerusalem. Micah 4:2 KJV
(19) Go ye therefore, and make disciples of all the nations, baptizing them into the name of the Father and of the Son and of the Holy Spirit: (20) teaching them to observe all things whatsoever I commanded you: and lo, I am with you always, even unto the end of the world. Matthew 28:19-20 ASV
And other sheep I have, which are not of this fold: them also I must bring, and they shall hear my voice: and they shall become one flock, one shepherd. John 10:16 ASV