I think we need to get some clarification from @mmiksell on exactly the goal here.
Based on the facts in your reply, you indicate "We have already acquired two more properties in 2021 and now meet all qualifications for real estate professional....."
The purpose of the aggregation provision is for real estate professionals to aggregate all rental activities in order to meet the material participation rule. I am not clear from your facts if you are a real estate professional for 2020?
If you are not a real estate professional for 2020, there is no reason to make the election for 2020.
If you are a real estate professional and make the election, Reg 1.469-9(g)(1) states "..In years in which the taxpayer is not a qualifying taxpayer [real estate professional], the election will not have effect and the taxpayer's activities will be those determined under §1.469-4."
Hopefully the above provides some guidance on whether or not 2020 is the appropriate year to make the election.
*A reminder that posts in a forum such as this do not constitute tax advice.
Also keep in mind the date of replies, as tax law changes.
