Ether is not in the currency business. It was emphasized multiple times by the devs themselves. It so happens that Bitcoin is so slow and full that users are flocking to use Ether as a currency even when Ether's inflation is uncertain. This is an open network, we cant stop people from using it the way they want it to.
Ethereum is not being built for financial apps only. It provides a VM that can run code and store data. This can be used for any purpose that requires code to be executed and data fields to be changed atomically in a secure way, the users need to pay a fraction of a cent worth of Ether to run this code. That means they dont have to be invested in Ether to be able to derive value from the Ethereum network. You have to be invested heavily in Bitcoin to get value from the Bitcoin network, especially after Bitcoin payments are such a dud. Please dont rush to type that Steam started accepting Bitcoin recently.
Ether is not competition to Bitcoin. Bitcoin killer will be a new token on the Ethereum network. There could also be a AirBnb killer and a Uber killer built on the network too. These are companies that pride on being leaders in sectors by writing only code. What if this code and data can exist as commons in the Ethereum network that is global and has 100% uptime. Users pay a fraction of cent worth of Ether to run transactions instead of a percentage cut. And these users will transfer money between themselves for these transactions with the token that killed Bitcoin, not Ether. It will take a while to kickstart a reputation layer on Ethereum network but these usecases are a real possibility.
There is a very good chance that these new tokens created on the Ethereum network will surpass the total market cap of Ether very soon :O