Back in 2005, the IOC held a vote on adding golf and rugby--two pretty British sports--to fill baseball and softball's spots on the program for the 2012 games in London, and they were rejected. So, London will only feature 26 sports instead of the usual 28.
It seems that there will always be battles within the IOC over the last two or three sports to feature in the Summer Games. So, the IOC should just do what they do in the World University Games and the regional Olympic-style events: have a large group of core sports a city has to hold--track and field, aquatics, gymnastics, soccer, basketball, and so on. Then let the host city pick two or three themselves to showcase, much like the old demonstration and exhibition events, only these would count.
It makes no sense for London to not have two British sports on the program, while Rio (and whoever wins 2020) has to go with golf and rugby sevens. One thing that would have been annoying if Chicago had won last week is that there wouldn't have been baseball on the program. Though as a Cub fan, I no longer have to worry about a momentum-killing month-long roadtrip (insert joke here).