American Jarrell Miller remains highly ranked, while compatriots Jared Anderson and Richard Torrez Jr, an Olympic silver medallist, are rebuilding.
New Zealand’s former world champion Joseph Parker is seeking a return after his provisional doping suspension was lifted in August.
Australia’s Teremoana Teremoana has stopped all 12 professional opponents within two rounds, while Uzbekistan’s two-time Olympic champion Bakhodir Jalolov extended his unbeaten record by beating Solomon Dacres on Saturday.
In Britain, Derek Chisora, 42, is considering another comeback and says he expects to face WBA ‘regular’ champion Gassiev in December.
British champion Richard Riakporhe is pursuing world honours after moving up from cruiserweight, while former cruiserweight world champion Lawrence Okolie is targeting a return after reaching an agreement with the WBC over an adverse drugs test finding.
David Adeleye, Dave Allen, Johnny Fisher and Frazer Clarke remain on the domestic scene, while Leo Atang, 19, and Ireland’s Adam Olaniyan, 20, are emerging talents.
With Usyk, Fury and Joshua approaching the ends of their careers, the heavyweight division is entering a new era.
There is no shortage of potential big fights, but bringing the champions together before mandatory obligations, rematches and boxing politics get in the way could prove the greatest challenge.