This last promise in Matthew extends beyond the life span of the Apostles to every believer that commits to the task of raising up a group of Christ-followers among every ethno-linguistic people groups on earth “to the end of the age” (Matt 28:20b). This phrase is also found in Matt 13:39-40, 49; 24:3, which refer to the end of the present age when the Son of Man returns to establish His kingdom. Thus the promise not only applied to these 1st century disciples, but to every disciple since then and until the end of the Church Age. We can count on His presence to empower and provide for the task.
"The Great Commission,"
2, Article 2.
Available at: http://digitalcommons.liberty.edu/jlbts/vol1/iss2/2