Genre: Sports/history
Title: The Shrinking Game
Estimated publication date: 2090 (perhaps in collaboration with any aspiring writers who are visiting my deathbed at the time)
This would be a book-length version of the (nearly book-length) post I'm working on, 'The Future of Popular Sports'. The general idea is how the history of rule changes in sports is a continuous trend favoring players of normal build. These changes usually emphasize the sport's specific skills or reduce the advantage of athleticism. Over time, the new rules allow players of relatively modest size, speed, and quickness to compete at an elite level.
Basketball provides many good examples. Its host of recent rule changes have made it harder for the tallest players to simply stand under the basket and wait. There are also good examples from soccer and helmet football which have reduced the advantages once enjoyed by physically imposing players. Every suspension for doping is a battle waged in the name of preserving the mean, median, and mode's prospects for sports stardom.
My book would then look at the current sports landscape, make some observations, and conclude with a few educated guesses about the sports which will become popular in the future.
The only obstacle to writing this book is a major one: I'm just not into sports enough. Putting a year or so of my life into a sports book project seems like a bit of a stretch given my current level of interest.