I think in the future there might be room for some sports to have leagues, similar to how boxing has weight classes but more holistic, which take into account everything including your natural hormone levels, VO2 capacity, bone density, height, weight, muscle to fat ratio etc to make the only remaining factors how hard you work and how good you are at the sport in question. But that's a sci-fi dream so for now making there be more stuff like couples' tennis would be cool.