The effect of this will be positive. In the first place this is an upgrade. With Shanghai upgrade, certain problems will be solved like delays. And this is in preparation for the Surge upgrade which will improve Ethereum's scalability. So this upgrade should not be perceived as a disadvantage.
Regarding the withdrawal of the staked ETH, it is not a problem. The amount of ETH staked is consistently rising. And if it rose when the withdrawal feature wasn't there yet, it will rise more because the feature is already there. Stakers won't worry anymore as to when they could unstake their ETH. So this Shanghai upgrade will boost more confidence and attract even more stakers.
Absolutely agree with this. The upcoming update will only increase the credibility of the ethereum network and this coin. If validators get the opportunity to manage their coins again, this does not mean that they will begin to sell them in bulk. Perhaps for some time we will get such a short-term effect, based on the fact that in some of them unforeseen expenses could arise during this time, but in general, such an update will only benefit the survivability of this network.