The main problems of Ethereum are high commissions and slow scalability - problems that EOS is solving better. But first of all the altcoins are tied to Ethereum and secondly it keeps developing, moving to Proof-of-Stake will solve lots of Ethereum problems (not all of them of course). For EOS there are still a lot of goals to reach but in future it will definitely be the main Ethereum competitor. I don't think any of these coins will die