We already have The Ender Dragon and The Wither but Herobrine has been in the game longer then both of them combined. He would have no armor but he would still be very tough like hes wearing invisible iron enchanted armor. He can teleport and has like the worlds strongest sword or they can add a new weapon that only drops when you kill him and thats what he uses. Next update (after 1.6) they should add Herobrine as a boss.