I predict this is the beginning of the end for Ethereum. First we will see what the intrinsic value of a blockchain is. Then the network will die when someone buys the 2/3rds of the validators for less than Visa makes in a day. It will probably just be Visa. Code is not law, money is. This is the core value on the network and has been for quite awhile now.
But lets assume you archive to controll 2/3rds of validators, you can not start staking the very next second. There is a queue (I think of some days) and people will recognize the attack before you will be able to perform it and people will simply blacklist you for their own sake.