The one-of-a-kind international competition was the only mixed gender event on the calendar.
Federer, along with Switzerland team-mate Belinda Bencic, won this year’s edition by beating German duo Alexander Zverev and Angelique Kerber in the final.
The 20-time Grand Slam winner also played against fellow legend Serena Williams in the group stages – in the first and probably final encounter of their careers.
The ATP Cup – a men’s international competition – will take the place of the Hopman Cup, starting in January 2019.
It was thought the Hopman Cup could possibly move dates to later in the year.
But reports coming from Australia suggest that will not be so, and Federer is distraught about the news.
“This is where it has always been, this is where the spirit is or was and will always be,” Federer said.
“It’s a bit sad news that it’s happening.
“I enjoyed the last three years playing there. I’m a bit torn.”
Australia’s head of tennis Craig Tiley is expected to announce the death of the Hopman Cup over the next 24 hours.
The new ATP Cup was revealed to the world during the ATP Finals in London last November.
And world No 1 Novak Djokovic gave his backing to the new season-opening event.
“I like that it’s owned by ATP, by the players, and that we have ranking points, and it’s going to be the best way to kick-start the season,” Djokovic said.
“Australia is a country that has a Grand Slam, that nurtures tennis tradition.
“More than 90 per cent of the time we’re playing as individuals and we don’t have too many team events.
“This is going to bring together a lot of nations and for me personally it will be a very nice and proud moment to represent my country.”