I think, give it time, there will be more use than there is at the moment for these in game currencies. When you look into your achievements you will see there is also a lower hauntlet achievement in addition to the upper hauntlet. Whether or not they will grant a different coin or not I'm not sure but the game is still developing very quickly and in a few months time we could all be thinking, wow we should have started farming these things a long time ago! lol

You never know what STS will come up with next?