The Olympic program is always changing and evolving (sorry about your removal in 1900, Basque Pelota), but there haven’t been many Olympiads that have seen as much change as the one between Rio 2016 and Tokyo 2020.
The Rio de Janeiro 2016 games saw 28 sports with 306 medal events, but that will move up to 33 sports and 339 events for Tokyo 2021. With new events in skateboarding, surfing, and karate, as well as the return of baseball and softball, there will be more events than ever before. But there will also be less total competitors: 11,238 athletes participated in Rio five years ago, while only 11,091 are so far expected in Japan.
Wrestling was originally scheduled to be dropped from this Games, but was returned by the IOC in September of 2013.
New events for Tokyo 2020
Archery (1): Mixed team event
Athletics (1): Mixed 4x400 relay
Baseball (1): (Men only)
Basketball (2): 3-on-3, Men and Women
Swimming (3): Men’s 800 m freestyle, women’s 1500 m freestyle, mixed 4 × 100 m medley relay
Cycling (4): The Madison (Men and Women), BMX Freestyle (Men and Women)
Fencing (2): Men’s Team Sabre, Women’s Team Foil
Judo (1): Mixed team event
Karate (8): (Kumite, three weight classes for men and women; Kata, men and women).
Skateboarding (4): (Park Men and Women, Street Men and Women)
Softball (1): Women
Sport Climbing (2): Men and Women
Surfing (2): Men and Women
Table Tennis (1): Mixed doubles
Triathlon (1): Mixed team relay
Dropped events from Rio 2016
Weightlifting (1): Weight limits changed, one less men’s class