When does Pekín Express return?

Peking Express is a Dutch–Flemish reality game show that follows a series of couples as they hitchhike to or from Beijing (only in the first three seasons; the following seasons are set elsewhere around the world. The theme of the show is to demonstrate how various couples deal with the challenges and pitfalls of attempting a hitchhiking to a strange city, together with all the difficulties presented by trying to communicate in a language they don't understand.