I also agree things probably wouldn't change much. I see and have seen people invest in newer coins, especially around 2017, but there's much less of those people than the majority that just trades the few large-cap coins like Bitcoin and Ethereum. I still think it'd be horrible if there were only 20 coins being traded, though, because the Top X coins changes all the time, for better and for worse. Just take a look at the screenshots on Coinmarketcap from years back.