Colback - reportedly a target for north-east rivals Newcastle - is a product of Sunderland's youth academy and first joined the club at the age of 10.
The midfielder, who was sent off on his Sunderland debut against Wolves in 2010, has been a mainstay in the side this season, playing 35 matches in all competitions for the Wearsiders.
Scotland international Bardsley was signed by former manager Roy Keane in 2008 and has made almost 200 appearances for Sunderland.
The former Manchester United defender, who enjoyed loan spells at Rangers, Aston Villa and Sheffield United earlier in his career, has scored four goals for the club this season.
The pair had been locked in contract talks with the club in recent months but manager Gus Poyet concedes he cannot see the pair extending their stay at the Stadium of Light.
"Everybody knows we have been in contract talks with a couple of players, but at the moment everything is on standby," said Poyet.
"Everyone is responsible for their own decisions and I don't think we are in a position to push people to do things they do not want to do.
"I'm not stupid, I understand it brings uncertainty to the club for the future.
"To be honest, it doesn't matter where we finish - I cannot see them staying at the club.
"It would be too easy to make a decision based on where we are (Premier League or Championship) because it would be very unfair on the fans."
A further six players, including Craig Gardner and Sebastian Larsson, are out of contract this summer and are also set to leave Sunderland with the club not offering them fresh terms.