I'm sure ethereum can last for at least 10 more years, the ethereum community is growing, look at the many ethereum-based projects that are worth up to billions of dollars and of course this makes ethereum even great.
Not only 10 years, ethereum will be in this market as long as smart contract's demand is going on. So, it'll long last for sure as we'll need smart contract for everything to do. Indeed, ethereum community is growing as well as more developments are on the dev's to-do list. Also, eth2.0 will be the best milestone. 
Ethereum, in my opinion, has become hostage to its advantages and disadvantages. What is the essence of this:
- The problem of network speed and the cost of transactions, these are disadvantages, disadvantages of which it is not yet entirely clear how to solve.
- ЕVМ and smart contracts are a very convenient tool, the most valuable for Ethereum. BUT! All of this today can already work in general without Ethereum - smart contracts have been successfully replicated on other platforms, and this exclusive advantage has disappeared from Ethereum. But the problems remain, and the new platforms no longer have these problems at the foundation level. That is why Ethereum can become a project that will kill the saby himself ...