What's new? These attacks aren't new for Bitcoin. But still, Bitcoin stands strong. It's not possible to move Bitcoin from PoW to PoS. Bitcoin isn't like Ethereum. Because Ethereum has a team who are deciding things and controlling everything as well. But Bitcoin doesn't have a team and miners have to decide. Do you think miners will ever support PoS? I don't think so since they are going to affect it in the first place. Just forget about technical things or how secure PoW is. Miners will never support PoS for Bitcoin.