The pair have had a testing season after failing to pick up squad numbers but still training every day with the Magpies to bolster day-to-day competition on the training field.
Bruce, who was about to hand Colback a squad place before late transfer window activity last August, said: "I feel for Jack a little bit and I wish him the best of luck.
"He's gone through a tough time.
"He took a horrible injury which he's over, I hope he gets on with his career, and Jamie, and they find a career for themselves.
"They are good pros and I wish them well."
United goalkeepers Rob Elliot and Nathan Harker are both coming to the end of their contracts.