Well, institutional investment companies have only been able to acquire around 1℅ of the circulating supply (particularly BlackRock). The rest is held by centralized exchanges, and self-custodied wallets. People just need to stop selling their coins to these entities to avoid monopolizing BTC in the long run.
Selling P2P or F2F (Face-to-Face) to another person ensures Bitcoin remains an equitable cryptocurrency for all. As long as the core Blockchain network remains decentralized, there should be nothing to worry about.
I doubt that investors will continue to self-custody BTC if they see the convenience and popularity of spot BTC ETFs. I don't think ETF funds need to self-accumulate BTC, they just need to secure the amount of BTC in their budget to be able to issue ETFs. They will buy and I believe there will always be people willing to sell in the market, problem is just price and volume.
I still believe that BTC will continue to exist in the future as a valuable asset, I'm just worried about investor sentiment: they may want something as simple as ETFs instead of having to do the complex task of buying, storing and protecting private keys.
