I think we should not switch to Proof of Stake system.
in Proof of Stake system, the one with more voting power tend to protect their investment and that will stop others from competing with them. they will use the voting power to make entering barrier, limiting the competition is bad for bitcoin economy (I believe).
Miners are not centralized, they just grow bigger and be industrialized, but there's still a lot of competition. The competition is the main security model of bitcoin system.
When we are talking about "security" in bitcoin system, we are talking about the probability that a transaction revert or change. We can not be 100% sure under 3 confirmations, but in 6 or more confirmations, we think the cash received is safe and can't be taken away. That's the security provided by bitcoin system.
Hard fork is not dangerous, when hard fork happens, people can wait for a short time (like maintenance of a POS/CreditCard system). When the chain with most hashrate wins (with high enough probability), we can then safely assume that the longest chain can't be reverted.