I believe that $1k during the 2017 Bullrun is the only highs that we are able to see in ETH history.
Agree. It looks very unlikely that developers would implement a hard cap in ETH's supply since the Ethereum blockchain has a long time since inception. It might do more harm than good as it'll require a contentious hard fork which I believe not everyone will agree with. With a limited supply, comes a higher price per coin. But considering that ETH was designed to be a platform for decentralized applications, having a higher price greatly defeats its purpose. After all, "gas" fees in ETH will rise like never before. It'll become costly in terms of USD for the end user to interact with a smart contract of his/her choice. For the good of ETH's adoption in the mainstream world, it's best to leave it as is.
Since we already have a limited version of Ethereum (called Ethereum Classic), there's nothing to worry about. Miners who want scarcity of coins on a smart contract platform would choose ETC over ETH. But everyday users will surely use ETH over ETC because of its greater accessibility for smart contracts. Until now, a high price per gas in terms of USD on the ETC blockchain is not an issue. That's because each ETC coin has a low price on the market. Expect to see reduced mainstream adoption of the ETC blockchain once prices start to rise above $2k because of the higher-priced gas fee in terms of Fiat for each interaction with a smart contract.
Nonetheless, it might be the case that ETH will rise no more than $1k per coin. It'll never be able to reach higher prices in the future as long as its supply is undefined. While that's good news for everyday users, it's not for the "hodler" or long-term investor. That's the case with inflationary cryptocurrencies like ETH and EOS. At least, ETH proves to be a solid smart contract platform that focuses on decentralization above anything else. Just my opinion