Why does nobody think he's going to defend his Chicago title next year? I would think his appearance fee potential here as an American and the defending champ would be greater than what he could get from NYC. If I were him I would do London in the spring and go for a fast time, then defend the Chicago title. Back to Boston in spring 2019.
Spring 2018 - London
Fall 2018 - Chicago
Spring 2019 - Boston
Fall 2019 - No marathon (some shorter races before prepping for OT)
Winter 2020 - Olympic Trials
Summer 2020 - Olympics
Fall 2020 - NYC (the 2020 Olympics is a little earlier than 2016, NYC is almost 3 full months later and if he wins another Olympic medal the earnings potential is too high to pass up)
Summer 2021 - World Championships Marathon in Eugene
After the 2021 Worlds I bet he retires, or if he hasn't won Boston yet maybe he runs that in spring 2022 and them hangs 'em up.