Johnson told BBC Radio Cambridgeshire: "He's been made an offer in Greece but he hasn't signed it and he's going to keep to his promise of coming back.
"He's going to talk to us on Monday and see where we are."
He added: "If he wants sunnier climates in December he'll choose Greece.
"If we wants to come through the mud and the blood he'll come to England."
We don't need Franck for this season anyway, but as a development of the team to compete in the Championship next time round would really be helpful
LtD
Johnson watched his side defeat Nottingham Forest 1-0 in a pre-season friendly at London Road on Saturday.
The only goal was scored by winger George Boyd, who failed to secure a permanent deal with Forest during a loan spell last season.
The Posh boss put out a strong starting 11, and then hinted it could be a similar side that will start the campaign opener against Bristol Rovers.
"I think it will be very close, but I think a couple of places are still up for grabs," he said.
Meanwhile director of football Barry Fry has revealed that Exodus Geohaghon, Dominic Green and Josh Simpson have all rejected moves to new clubs.
The trio have been told they are surplus to requirements at London Road.
Source: BBC Sport
Source: BBC Sport