I know there are a LOT of debaits about how supercell said a new hero was possible. The three most popular ideas I've heared are Wizard, Dragon or Goblin. I feel like Dragons are the best choice because
a) A resource-stealing hero would be just plain annoying, like a mortar-proof goblin.
b) A ranged, splash damage dealing hero that has like 230 damage to start is no fun it also has the potential to flat-out destroy storages and things around it "Dang!! 400k gold gone in under 10 seconds!" Also think of how easy farming would be: drop a couple leagues and farm like crazy! It would give birth to strategies like: 1 Golem 1 Archmage (wizard hero) 300k resources.
c) Dragon Emporer (like my username XD) would be nerfed by massive costs (possibly feeding Dragon Emperor Gold and Dark Elixer like X-Bow and Inferno Tower).