I can't guarantee Ethereum will last forever, but for the next 2 or 3 years they will remain at the number two position, so far there is no capacity for another coin to replace it.
If we're honest, the odds against Ethereum are currently very heavy and impossible, ethereum has a lot of advantages at the moment, compared to other coins. More and more people are starting to believe in it and as evidenced by the many choices that are given to people today, it is not fundamental to say that Ethereum will be replaced in the near future.
It's very unlikely Ethereum will disappear anytime soon, since no other competitor has been able to take its place on the market. The world's second-largest cryptocurrency by market cap is similar to Bitcoin with a proven track record of development and innovation. Being the pioneer of smart contracts, Ethereum has obtained first-mover advantage in the world of altcoins.
Now, how long will it last will greatly depend on how far people are willing to let it go. The number of nodes, miners, developers, and individuals have been constantly growing since the network's launch in 2015. Set yourself forward 5 to 10 years from now, and Ethereum will be a much bigger ecosystem than what it is right now. Until a strong competitor comes up, Ethereum will remain the dominant force of the market (after Bitcoin) for a long, long time. Just my thoughts
