“Game of Thrones” fans, brace yourselves: The fantasy saga’s end is perhaps just a few years away. HBO programming chief Michael Lombardo said Thursday that the drama series’ producers are leaning toward three more seasons after the just-concluded season five. Asked about the possibility of a prequel series, Lombardo said he believed there’s “enormous story material” to be mined for such a project. Lombardo was asked if the popular character of Jon Snow, who appeared to die last season, was actually a goner. Lombardo said, “Dead is dead is dead.”