The Ivorian left the Swans for the Etihad Stadium on a four-year contract in 2015 for a fee worth up to £28m.
Bony, 28, managed only eight goals in 46 appearances for City - more than half of which came as a substitute - and spent last season on loan at Stoke.
His potential return to Wales could depend on the future of Swansea's top scorer last season, Fernando Llorente.
The 32-year-old, who is currently sidelined with an arm injury, has been a transfer target for Chelsea, having worked with the Premier League champions' manager, Antonio Conte, at Juventus.
Swansea have yet to receive a bid this summer for the Spain international, who scored 15 goals last season to help the Welsh club avoid relegation from the top flight.
The Swans did reject offers for Llorente during the January transfer window, and a move for Bony could be seen as insurance should Llorente leave.
Swansea signed England Under-21 striker Tammy Abraham on a season-long loan from Chelsea earlier this summer.
But with club record signing Borja Baston on loan at Malaga, the Swans could be short of forward options if Llorente was to leave.
Before Baston's arrival, Bony was Swansea's record signing when he joined from Vitesse Arnhem for £12m in 2013.
He scored 34 goals in all competitions for the Swans before his move to City.
Bony's high wages at City were thought to be a stumbling block for a potential return to the Liberty Stadium, though Swansea could soon have more money if midfielder Gylfi Sigurdsson joins Everton.
Swansea City are weighing up a move to re-sign striker Wilfried Bony from Manchester City.