I think as more and more insurrectionists get sentenced to federal prison, and other Republicans start to suffer consequences like disbarment, a lot of Trump cult followers will decide it's not their patriotic duty to commit sedition. By 2022, if the Trumpistas are still the majority of Republicans, moderates will get primaried. Then the whack-job candidates will mostly lose in the general election. So Democrats will capture more seats in both houses. If they don't get primaried, Trumpistas will boycott the general election, and Democrats will win more seats.

This will not follow the usual midterm seat loss paradigm, but seldom has the party out of power been so fractured.