From what I am reading and hearing about it, the IRS is going to start processing right away so they will probably initially view your 2019 and you won't get one. However, the are SUPPOSED to look again after you file the 2020 and if your income is lower they are supposed to update the records and send you a check once that second review is done. Unfortunately you're at the mercy of the IRS on this one (and I hear they are so backed up they are still processing 2019 returns). So if you can't get 2020 filed right away, I would just file when you can and hopefully they'll put in a process where you can request a check after that lower AGI is done. If I hear anything differently I'll PM you.
Good luck and Hail State!
Good luck and Hail State!