The two fighters have begun negotiations about a 2018 showdown this week after Wilder beat Bermane Stiverne on Saturday.
Previously Joshua saw off the challenge of Carlos Takam, opening himself up for a fight of his choosing.
And Hearn claims the 28-year-old Brit is too humble to threaten Wilder, but he fully believes the Londoner will extend his 100 percent knockout ratio when the two meet at the turn of the year.
“He’s not the type of guy to come out and say ‘I’ll knock Deontay Wilder out.’ He knows he will and he will,” Hearn told BoxingScene.com.
“He believes it, but you won’t hear him say it, because he’s humble and he’s not gonna change
“I’ll say it. Anthony Joshua knocks out Deontay Wilder every day of the week – including twice on a Sunday.
“But there is no point in talking about until we sit at the table. The good news is for fight fans – is that process is starting.
“And the good news is for fight fans – is that fight will happen in 2018.”
Hearn watched Wilder beat Stiverne and believes that Joshua has nothing to fear when the two go toe-to-toe.
“I didn’t learn anything new,” Hearn added.
“I don’t think that you can possibly learn anything from that fight that you didn’t already know. Deontay Wilder is a reckless, big puncher. If you want to give him props for beating Bermane Stiverne … a guy who didn’t throw a punch in the fight, a guy who boxed like once in three years…. not really.
“But he dealt with his mandatory and he dealt with it impressively.”