It could potentially lead to a run on Ethereum. The resource used in PoS is the cryptocurrency being secured itself. Basically, you agree to lock up a certain stake when you run a validator, and forfeit it if it's found that your validator "cheats". By doing this, you make cheating unprofitable - there's a financial incentive to catch cheats, and a financial disincentive to cheat, and the cheaters eventually go bankrupt (or end up on their own isolated chain where nobody transacts with them).
The financial effect of this is that a bunch of Ethereum gets locked up and illiquid. Instead of miners receiving Ethereum which they want to sell for dollars to run their hardware, stakers lock up Ethereum and effectively receive interest. This reduces immediate supply within the market. I'm wondering if a lot of the recent price movement is in anticipation of this.