As both Fury and Usyk are in their best forms right now, if I were them, I would force event to have a fight. The winner will get all 4 major belts and will be best of the best in heavyweights. Waiting means loosing chances to become the one with all belts. With current pandemic situation, as coin-investor said, it will take years before these two will meet.
As I understand, Fury has not contract obligatory to fight anyone. But Usyk must either prepare for Fury and try to get all the belts and face financial consequences for not having a rematch with Joshua. Or put the idea of obtaining all 4 belts on a higher shelve.
Seeing it from that point of view, the one who has the most pressure is Usyk, because the others do not need to show much, but I have seen that Usyk is more hungry to win than to be the best, to show the world that he cannot leave without facing the best , it is very easy to pretend that you can win everything without having faced the best, that is like having a title with almost no effort, which does not have much relevance, well that is how I see it and I think any fighter too . This reminds me of Pacquiao's fight with Myweather, when after the match Myweather what he did was run away from the Filipino, he told him that he didn't want any more revenge, which seemed to me to make him afraid of a possible second match.