Jesus came to establish the Kingdom of God. That is the core of His teaching and the reason for the cross. When He left this earth He called on His followers to devote themselves to the task of extending the influence of His Kingdom beyond the borders of Judea – even to the ends of the earth. That pretty much covers all of the various people groups in our world. The King has never repealed His edict. His followers are still called to be devoted to the task of expanding the influence of His Kingdom today.
As we experience a huge influx of refugees and immigrants in our own community, we really do not need to go far to discover another "people group" – not to mention an expanding culture we label as ‘post-moderns’. They are our neighbors, our fellow workers, and kids in our classrooms. They are a new generation with a vastly different cultural paradigm than that of the traditional institutional church of the 20th century. If we are going to continue to follow Christ in mission, we are going to have to be re-tooled.