Yeah, I am worried too as I had planned to apply for 2021... Did you get any insights elsewhere?

Indeed, I am also a bit worried because I was planning to apply for a 2021-2022 LLM.  I heard that deferrals due to Covid-19 are now very common for US-based LLM programs. If so, will the number of available places for applications submitted in the fall of 2020 shrink? 

If anything I think the opposite would be true: since there are more deferrals than normal (at least for this application cycle): there will be a lot more open seats and law schools would subsequently send offers to candidates they wouldn't necessarily have sent them to in other years. 

For the next fall intake (2021) it's too early to tell. If the pandemic is more under control (or if there is less uncertainty) then a lot of those who deferred this year would probably take seats. In that case admissions would be more competitive due to fewer seats being available for new applicants.