Promoter Eddie Hearn is working on the fight, which would be worth even more than their £40m Wembley thriller last month.
Heavyweight champion Joshua is also set to retain the IBF belt if he faces the Ukrainian again, despite fears he could be stripped.
But should Klitschko retire then Joshua will face mandatory challenger Kubrat Pulev, most likely at the Principality Stadium in Cardiff this Autumn.
Klitschko, 41, is on holiday with his family and will decide his next move when he returns.
Hearn said: “If Klitschko comes back and says he doesn’t want a rematch then we will fight Pulev next, unquestionably.
“I spoke to Klitschko’s manager Bernd Bonte a few times.
“Bernd said he (Klitschko) will have two weeks with his family and then he will make his mind up.
“I am looking at options now for the rematch while we wait on Klitschko because you have to have an idea on dates and possibilities.”
Source : EXPRESS