To be a disciple of Christ is to follow him; that could only be done literally while Jesus was on earth. After he ascended back to heaven, no Christian could follow him in a literal sense. Yet they continued being his disciples by continuing to follow his teachings and his ways.
A second sense of discipleship is to teach others the ways of the Great Teacher - Christ. That can only be done by those who have been taught by Christ, who have sat at his feet. Literally so while he was on earth (Mary, Luke 10:42). She was being discipled by the Lord himself, and so chose the better portion than did her sister, Martha. But after Jesus returned to heaven, discipling continued. The apostles taught pubicly and in the homes of believers, so that those ones who came under the sound of their gospel teaching became followers also. Yet not every believer is called to be a teacher, as were the Apostles. Did that prevent them from being disciples? Of course not! They were taught, and believed, and went into the world to commend Christ to others, by word and deed.
They need not leave their home village to do that, of course. They did not have to become itinerant preachers. If that was what was necessary to be a disciple of Christ, would that mean ceasing to be a disciple when thrown into prison? After all, no traveling about could be done then, and that could go on for years. Consider the apostle John, languishing on the isle of Patmos. Did his incarceration there prevent him being an itinerant disciple? Of course not! There's more than one way of following Christ's commission to "Go ye, therefore, and teach all nations... teaching them to observe all things whatsoever I have commanded you" (Mat.28:19-20). John was able to continue his ministry by writing - consider the book of the Revelation, penned by him in his old age!
Nowadays the itinerant ministry can still be done while sitting at home, using the Internet. Or it can be done over the garden fence, speaking about Christ to a neighbour. It's not location, or clocking up travel miles that makes a disciple itinerant. Discipleship has never ceased; it's just that making disciples has gone on throughout the centuries, but is not confined to personally visiting geographic locations. Since the advent of the printing press, postal systems, telephone and the Internet, it's just become a global outreach that disciples of Christ can use to share the gospel and teaching of Christ without being confined to the very limited means the disciples were stuck with in the first century.
All who follow Jesus find ways of sharing the good news of him with others; such followers tell others, and so more disciples result. It's just that discipleship, as in the gospels, has now expanded to what those first century disciples could never have dreamed of.
