New Zealand will play last year's World Cup finalists Samoa and Australia in the Pacific Championships in October and November.
Johnson, who played the last of his 32 Tests for New Zealand in 2019, has been in career-best form at halfback for the New Zealand Warriors in their surge into third position on the NRL ladder.
The 32-year-old missed out on selection for last year's World Cup but Maguire said the playmaker had the desire to play at the highest level again.
Whether that is this year remains to be seen.
"Shaun is going to assess that when the time comes and see how his body is," Maguire said at the launch in Brisbane of the Pacific Championships.
"His big focus at the moment is obviously trying to win it for the Warriors but it has been nice to see how he has been playing.
"Shaun was obviously disappointed at the back end of last season and obviously didn't come away to the World Cup.
"One thing he did say is, 'I will be back. I want to have another crack at the international space'."
Maguire said Johnson understood form was the criteria to make the Kiwis side.
"He has obviously backed that up with the way he has been playing," Maguire said.
Maguire said the Warriors' surge into the top four of the NRL had been "enormous" for the game in New Zealand.
"I was just talking to (Cook Islands coach) Tony Iro about the number of kids coming through. He said they've just had open trials and for each age group they have 400 to 500 players coming through and that's fantastic," he said.
"The Warriors have taken the game to a whole new level in New Zealand."
The Kiwis lost their World Cup semi-final last year to Australia and the pain still lingers.
"We had a bit of disappointment over at the World Cup. We had our moments in the semi-final but I think (that loss) sits inside of me, the staff, the players and the organisation," Maguire said.
"To be able to get the international game back, to get the momentum back and play against Australia and Samoa ... we are looking forward to it."
