I do think it's a bit too early to say, honestly. He's shown up in one episode, for maybe twenty minutes. We have no idea what his motive is, beyond boredom, or what any of his future plans are.

That said, I wouldn't be surprised if he was some sort of bluff. There were, after all, two James Moriartys and a third (probably also James, going by ACD's track record for such things) Moriarty running around. Gatiss and Moffat seem like the sort to exploit that in some way.