Mr. Shiftlet is a drifter and his actions at the end, abandoning Lucynell and taking off on his own, are foreshadowed in the story. First, in his initial meeting with Mrs. Crater, he describes his past, noting that he had traveled extensively and "visited every foreign land." He had held many jobs in his life including "gospel singer," an undertaker's assistant, a railroad foreman and a soldier. This is a good hint that he will not be happy permanently staying on Mrs. Crater's property.
Second, his immediate interest in the Ford automobile signals to the reader that the car will take on an important role later in the story. At the end, after fixing up the car, he steals it and heads off to Mobile. He leaves Lucynell asleep at a roadside diner, an action he had presumably planned ahead of time. Third, as he bargains with Mrs. Crater over what it will take for him to marry Lucynell, he compares his spirit to the automobile:
"Lady, a man is divided into two parts, body and spirit...The body, lady, is like a house: it don't go anywhere; but the spirit, lady, is like a fine automobile: always on the move, always..."
While he suggests throughout the novel that he would really like to settle down "where I could see me a sun do that every evening" he's also likely to shift his sentiments, as his name suggests. The drifter part of him is always moving, even as it seems he has found what he was looking for, land and a girl who is described as an "angel of gawd." He readily dumps Lucynell to satisfy his wanderlust.