During the Ethereum Core Developers meeting on December 8, Ethereum devs said the Shanghai fork could come as early as March 2023. This is the Ethereum fork that will allow investors to withdraw their staked ETH and staking rewards.
The Ethereum blockchain transitioned to Proof of Stake consensus when it completed The Merge a few months ago. Ethereum devs created a way to stake ETH to help the network operate, but they never released a mechanism for withdrawing ETH after staking it. The Shanghai fork is a software release intended to solve this issue.
Roughly 14% of all ETH is staked, and a lot of that ETH has been locked up for over a year. Ethereum devs were concerned about a mass selloff following the Shanghai release, so they set a limit on daily withdrawals. It's looking like only 43k ETH can be withdrawn per day out of ~10M total staked ETH.
In the end, I don't think there will be much of a selloff following the Shanghai fork, because a lot of the weak hands already sold at a loss using liquid staking tokens that represent their staked ETH.