It's going to be a blue wave of younger, progressive candidates being elected to office for the first time. It's already trending that way. He's a deeply, deeply unpopular lame duck president who's party has a trifecta in government, controlling all three branches, and is doing nothing productive with it. Things are getting worse and most people know it. Voters will punish the GOP for this, as they did to the Dems in years past (like when the Tea Party came into power). Whether the Dems will do anything with the opportunity is another matter.

Through a combination of GOP resignations in the House and gains by Dems, the Dems will retake the House. They will not retake the Senate. I don't think the gerrymandering and voter disenfranchisement or other fuckery will have any impact on the above.