It seems that one of the chains will fail over time. The question is, which one?
What do you mean by "fail". ETC is moving and trading. It may be declining but it still has supporters. They will both run for a long time. What's more important is who will support which chain for what purpose and what value will that bring?
If you really think one chain will die then right now ETH has the advantage. Why? Because it has more hashing power. ETC's hashing power is only about 10% to 15% that of ETH. If one chain is truly dying then it is ETC. Please observe the chain state here
http://fork.ethstats.net/Price and volume in the exchanges should not be used to judge if ETC will continue or die. The answer lies in the hashing power.