Source: BBC Sport
Calzaghe's promoter Frank Warren said: "The deal's done and will be confirmed with the venue and date next week."
The undisputed world super-middleweight champion said: "The talks with Hopkins' representatives are almost over, and I've been told it's on 12 April.
"The venue is not set in stone but it does look like the fight will be in Las Vegas," he told the South Wales Argus.
Hopkins, 42, is widely regarded as the best light-heavyweight in the world, and Welshman Calzaghe will step up to 175lb to meet him.
The most solid rumor about the venue has been the Mandalay Bay Resort and Casino. Talks to put the fight in New York City were trumped, according to the BBC article, by Vegas offering more hotel accomodations, as many from across the pond are expected to "invade" Sin City the way they did for Ricky Hatton's fight against Floyd Mayweather, Jr.
The atmosphere should be electric, particularly if a good portion of the audience is Calzaghe supporters. And I think the fight will be a gem for those that enjoy the chess match style of boxing of which Hopkins and Calzaghe are both excellent practicioners. This is a fight that will almost certainly go 12 rounds, and I think most of us expect it to be a tight one. It could also be the last time we see Hopkins, particularly if he loses, and it could very well be the last time we see Calzaghe, if we are to believe that he's truly ready to end his career after one or two more big fights. And this one, make no mistake, is the biggest of his illustrious career.