Overall, I think the impact is quite limited because most interviewers will already have their favoured case(s) that they are using with candidates and no real reason that this will change in most instances.
However, I think there is a chance that for more open-ended cases, especially in a partner round there could be questions related to the corona situation and how it's impacting the economic situation. For example, I had a mentee applying for Strategy& who got a question around what industries he expects to get most impacted by the COVID-19 situation in his country and which ones would be fastest to recover.
With this in mind, it would make sense to stay up to date with news and reporting about the virus along with reading some reports that the MBB are publishing frequently.
Hope that's useful!