How will Covid-19 affect SAT and ACT?

No one really knows right now, and we likely won't know for sure for quite a while. I know that's not a satisfying answer at the moment, but it's the best I can really give you. A lot of this depends on what happens with quarantine in the next few months, if we can successfully move to a strategy to contain the virus, and on the timeline for a vaccine to be developed. None of which I know much about besides the basic, publicly accessible info.

The likeliest scenario though is that a lot of the schools currently going test optional for the Class of 2021 may remain test optional into the future, and this might accelerate an already growing shift towards test optional policies at a lot of schools all across the board. The tradeoffs with test optional policies are that, if you can do well on the SATs/ACTs, you can still give yourself a significant advantage with a strong score. But if people aren't able to take those tests, they can still get a fairer assessment that will weigh more heavily on their GPA and coursework for an academic evaluation.

I do think online SATs and ACTs are somewhat likely farther into the future, but creating that kind of infrastructure takes a lot of time. It would likely be harder to move the SATs online than AP tests, since SATs are more centralized and since many more students take the SAT than do AP tests. Right now, I would assume that the situation for 2022 will likely be pretty similar to what 2021 is experiencing right now.