After 2017, If Bolt doesnt retire, the Brojos should put money on the line for that sub 5 mile effort.
With TV (or at least youtube) live coverage. Because Letsrun is, by now, the most popular track/field/running forum on the web.
Advertisers and sponsors would support the idea without hesitation.
In a meet before April (when Bolt is doing his aerobic phase) in Jamaica UWI track.
As a die-hard track fan, I think that would be the biggest event of the 2018 season, featuring another challenges like:
Mo Farah doing the 400m (with extra incentives for running under 49 seconds)
Elaine Thompson running the 800m
Discus throwers doing High Jump or 110m Hurdles