I could see Kings Island bringing back smaller things for their 50th anniversary. Things like the Coney Mall sign, the Oktoberfest sign, the large ivy tunnel, and old food items could be brought back. I could also see them repainting The Racer to its original color scheme and focusing on older rides. Other things Kings Island could do include building a new restaurant, adding a legacy walk, or maybe bringing back a smaller ride like Der Spinning Keggars or re-theming Boo Blasters to Phantom Theater. Those are probably more unlikely though.
In terms of 2021, I would like to see shows return as well as full trains and all trains.