Ever since Ethereum was created in 2015, the whole crypto/Blockchain space improved in many ways that were never imagined. The ICO trend of 2017, and the current "De-Fi"/NFTs hype are all attributed to Ethereum's ever-rising popularity in the mainstream world. If it wasn't because of Ethereum, we wouldn't had a plethora of smart contract platforms to choose from. The crypto/Blockchain space would've been focused solely on finance, instead of serving as a hub for decentralized applications.
It's been 6 years since ETH came into inception, and now the smart contract platform is the second-largest blockchain network in the world. Some people compare ETH to BTC because of its focus on decentralization unlike any other cryptocurrency on the market today. As of this date, Ethereum has a large number of miners and nodes keeping the blockchain alive and healthy. If ETH continues to grow, it could live alongside Bitcoin for many years. But we all know that nothing lasts forever.
What's your opinion on this? Will Ethereum last forever? Or will it eventually die? Do you think it'll retain its place as the second-largest cryptocurrency by market cap for long? If not, why? Do competitors stand a chance against ETH? Your input will be greatly appreciated. Thank you.

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.