"If every Christian is already considered a missionary, then all can stay put where they are, and nobody needs to get up and go anywhere to preach the gospel. But if our only concern is to witness where we are, how will people in unevangelized areas ever hear the gospel?"
The Great Commission is taking the Gospel to our Jerusalem. This is where we live. It is where most of our time, efforts and ministry are centered. But Holy Spirit empowered believers are likewise charged to be His witnesses to their Judea, Samaria, and, yes: the ends of the earth--the nations.
When we begin to move beyond our Jerusalem and seek to engage our Judea, Samaria, and the nations--then, we become misionaries--the sent ones that we are meant to be.
I believe Jesus intent was for us to be fully engaged in all four regional dimensions of the Great Commission. Too many have deceived themselves into believing they "aren't called to missions." Really? It would seem the burden of proof would be more on the side of our being NOT CALLED to engage the nations. For too long, disciples of Christ have excused themselves from doing what Jesus commanded simply because they have chosen to live a life to their own pleasing. It has nothing to do with anything God might be asking of us and His call on our lives.
When we lose sight of just how serious our Lord was about Acts 1:8 we run the risk the disobedient Jerusalem church ran into in Acts 8:1
"And on that day a great persecution arose against the church in Jerusalem; and they were all scattered throughout the regions of Judea and Samaria...those who had been scattered went about preaching the word..."
It took some serious persecution allowed by the Lord himself to get them to obey, and engage their Judea, Samaria, and ends of the earth. In our present imbalance of uneven distribution of Christians, do we not think the same could again happen today? Just how serious was our Lord when He commanded us to "make disciples of the nations?"
So everyone may indeed NOT be a missionary, but it is my belief that we should deliberately seek to do everything in our power to make sure we ARE missionaries.