Assuming these factors are set in stone for 2022...

[ChiefFireWaterMike]

I think 2022 will be like 2002 -- Democrats gain more House seats. What will happen in the Senate is harder to tell, because we don't yet know the outcome of the two Georgia races.
(BTW, I don't think you can treat the 1978 election as a neutral outcome; Republicans gained 15 more seats in the House, bumping Democrats out of their two-thirds majority they had won in 1976.)

Where are they supposed to gain them tho? Even in an environment comparable to 2020, Democrats would probably lose the House considering the fact that gerrymandering in populous states will likely hurt them hard (FL, TX, Jim Cooper's district in TN, RI-02 gets abolished, and CA has a nonpartisan commission to draw maps).

California's commission will most likely be "nonpartisan in name only."

This