If the new Dem president gets reelected and it's not a huge landslide, I would expect that Democrats don't pick up the House until the 2030 midterms.
In this scenario, the GOP will have controlled the House for 20 years.
In general, I don't think its very likely that the Democrats beat Trump but lose the House. This isn't the 70s and 80s. If they don't have enough votes, they don't have enough votes. No one president was able to win without SOME downballot succes since Nixon and he might be the only one.