Yes, this would impact the next election cycle, occurring in 2022, and the effects would first be seen in the congress sworn in in January of 2023.

The states with changes in seats are responsible for the redistricting. What this means in practice is that in a state losing one seat, one district will disappear and the map gets redrawn. Then you'll typically have a primary or a general election where both candidates are incumbents. If both incumbents are in the same party, they'll face off in the primary for that party, if they're in different parties they'll face off in the general election. Alternatively, one incumbent may choose to retire.