AJ and Fury had put pen-to-paper on the super-fight that would have crowned the first undisputed heavyweight champion since Lennox Lewis.
However, the Gypsy King will now face Deontay Wilder this summer after a court of arbitration ruled in his favour regarding a rematch.
It means Joshua, who currently holds the WBA, IBF, WBO and IBO belts, will need to change his plans for 2021.
WBO have ordered AJ to fight mandatory challenger Oleksandr Usyk, with a deadline of May 31, set to strike a deal.
Matchroom boss Hearn has admitted a fight against the Ukrainian is the most likely at this point, although negotiations must make sense for all parties.
“We have 10 days to negotiate that fight, after those 10 days, if we haven’t agreed a deal, purse bids will be called,” Hearn told iFL TV.
“They’ve ordered a maximum split of 80/20 and sent some bout agreements to finalise what the split will be and then we’ll make a final decision on the fight.
“I think there’s a deal to be done for that fight, I think that’s the most likely of the next few options.”
He continued: “In an ideal world, if there’s good business to be done with Oleksandr Usyk, it’s got to be good business for him as well, that’s the fight next.
“I wouldn’t rule out any scenario at the moment for Anthony Joshua. We’ve probably got 10 days to decide what we’re going to do.”
Hearn did claim that there are other options on the table and if he was to look at a fight in America, it could see him face old foe Andy Ruiz Jr.
The American stunned the world in June 2019, after he stopped Joshua to win four versions of the heavyweight crown.
Joshua would beat him comfortably in the rematch, but he’s keen for one more crack in what would be a trilogy completing bout.
On other opponents for AJ, Hearn continued: “There’s quite a few. If you’re going to America, he’s already messaged me, it’s like deja vu, Andy Ruiz.
“He messaged me on Instagram and said: ‘I’m ready, let’s do this, AJ v Ruiz three’.
“That’s a fight I think we’d be interested in, if you’re going to America, Luis Ortiz is another guy you could fight.
“If you’re doing the UK, I don’t know…Dillian Whyte, that’s a fight to make.”
Asked if there was a chance that Joshua could relinquish his WBO belt in order to go in a different direction to Usyk, Hearn added: “Only comes down to business, if the deal’s not right financially.
“I spoke to AJ last week and we’ve already had these conversations with AJ and Rob McCracken over the last year or so about Usyk, more than happy to fight him.
“Anthony Joshua has continuously faced everybody he’s had to face. He’s more than happy to fight him, it will just come down to business.”