It's a temporary state, until the PoS coin market cap gets too large to be attackable. Bitcoin's market cap is in the 1T range now, Ethereum is close to half that. Buffet couldn't do a thing against a PoS coin that large, and it would be a serious commitment and risk even for a nation state. Buffet could take down some random smaller coin, maybe, at the cost of most of his personal fortune, but if he did so the world would not burn.

It's _possible_ that a government might choose to attack a random small coin just to discredit the notion of PoS cryptocurrencies, but it's hard to picture a government gaining consensus to do it, and it would be obvious to knowledgeable onlookers that larger coins are immune (or anyway, much better protected), so the resulting disruption would probably be temporary.