I would definately think of it as a multi-dimensional title. Regardless of its original meaning, it can be interperated as Anakin, Luke, or the Jedi in general returning. However, as to what Lucas meant by the title, I am 95% sure he meant it as the Jedi as a whole, not as a single person. Over the years the whole concept of Jedi and Sith has evolved to allow us to realize more meanings than that, but originally it must have just meant the group/order.