They only viable way for ETH to catch up with bitcoin would be situation where bitcoin development would be halted, scaling issues never addressed.
In short: if current idiocy of supporting Bitcoin Unlimited will continue for years then ETH will have chance.
But in the moment we will have SegWit and Lightning Network operational, BTC will be complete.
I think this is the only thing needed to shut down ethereum from reaching Bitcoin status or overtake it the sooner it is implemented the sooner this will happen,altcoins are moving to catch Bitcoin because of these issues.
There is a point on which i agree with BU guys, Bitcoin core needs new features. Actually smart contracts is the most demanded features, but there are many things that be added on the Bitcoin blockchain.
Some of you may know about OP_RETURN sigop, this is what is used by counterparty and omnilayer to create assets bound to bitcoin addresses. Not only this sigop but it is a part of their solution. This is the way Bitcoin stores informations, so anyone can store messages, functions and things on bitcoin blockchain. The difference is that you can't execute it directly from the blockchain. you can retrieve it, parse it (because it is saved in HEX format) change it, and then work with it.
At least the basics for such features are aleready implemented.
Now regarding Ethereum, he will never overtake Bitcoin because it is not unique, there are a bunch of other projects who are implementing smart contracts on their chains which is the main HYP argument for Ethereum.