The details have been in place for a fortnight, awaiting only the 41-year-old Klitschko's commitment to carry on in the ring, which has seen him trigger the rematch clause.
A farewell fight in Vegas - the fight capital of the world - is believed to have clinched his agreement. So powerful is the lure of Vegas that Klitschko has turned down a bonus payment in excess of £1.5 million ($NZ2.6 million) to fight under the Principality Stadium roof in Cardiff.
That less glamorous option would have given Joshua home advantage as huge as that which rescued him from impending defeat at Wembley Stadium in April, when he survived a knockdown to eventually stop Klitschko in the 11th round.
Win or lose, this is likely to be Klitschko's last fight and a source close to his camp said: "If this is to be the end of his fantastic career, he wants to go out in style in Vegas."
The financial disparity of an 80,000 crowd in Cardiff and the 20,000-seat arena in Vegas will be covered by an expected increase in pay-TV sales in America.
Joshua's willingness to go again has never been in doubt. He is looking to expand his marketability into America.
Thus he has been in Vegas in the past week, looking at the venue and setting up the facility to train at Floyd Mayweather's fabled gym.
He is also expected to be at ringside for Mayweather's showdown against UFC fighter Conor McGregor next month.
Hearn said: "It will probably take a couple of weeks to get this over the line but I believe Klitschko in Vegas is the one."
Among the details to be finalised is whether one or both of the major US cable television networks acquire the broadcasting rights there. In an unusual move, both Showtime, with the live transmission, and HBO, with the tape delay, screened the Wembley original.
That was made possible by the time difference between Britain and America, which enabled a live afternoon screening in the US, with the replay the same evening.
The original plan was for the rematch to take place in a football stadium in Ukrainian Klitschko's adopted Germany, with the two US companies switching roles.
Now they may bid against each other or agree for HBO to go live, leaving Showtime to pick up the repeat audience in the days following November 11.
Either way, a prime-time fight will draw a much bigger subscription audience. Joshua will again be favourite to beat the veteran, who reigned as world heavyweight champion for more than a decade.
But another incentive for Klitschko is his belief that he would have beaten AJ had he gone for the finish, after knocking him down in the sixth round of the first fight. Brother Vitali, also a former world champion, has apologised for advising him to husband his strength and ease to a points decision.
Hearn, who conducted his Vegas negotiations under cover of a trip there for Matchroom's darts productions, added: "It will be another momentous occasion."
