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.