I don't think the when, where, or how many debates has been decided or agreed on yet by the TRUMP/Biden Teams.
Tucker Carlson is just running his mouth and flapping his forked tongue!
Trump has sent mixed messages on the subject of whether he will debate Biden.
The New York Times reported late last year that Trump had raised doubts around the debate, stating that he did not trust the Commission on Presidential Debates–a nonpartisan entity. He later wrote on Twitter that though he wanted to debate the Democratic nominee, he was concerned that the Commission was "biased" against him. "I will make a decision at an appropriate time but in the meantime, the Commission on Presidential Debates is NOT authorized to speak for me."
More recently, though, Trump has indicated that he will debate his opponent. "Yeah, sure. I look forward to it, actually," he told reporters in February, when asked.
And in June, Trump campaign manager Brad Parscale and Rudy Giuliana requested a fourth debate between Biden and Trump, which, if granted, would add one more to the schedule.
That said, given the President's history of inconsistent and self-contradictory messaging, there's no real way to know what he'll decide by the fall.