Sibierski joined last season on a free transfer and was credited with the goal of the season for his volley against Chelsea at the JJB Stadium.
Meanwhile, Bent has re-joined Charlton after his loan move came to an end, A deal of £1 million is in place, but the Latics may not take up the option.
Bruce is said to be chasing Egyptian Amr Zaki and Reading's Dave Kitson instead. The Zaki move is said to be nearing completion after his club Zamelek relinquished their hope of keeping hold of the striker.