Kerr still has another season left on his current deal but has impressed his manager with some solid displays in important games this season, while Caldwell is out of contract in the summer and is attracting interest from Rangers.
Sir Bobby said: "Kerr has made a real spurt over the last four months and I see him as a first team player.
"I also want to keep Steve Caldwell whose contract is up in the summer."
It will be interesting to see if, with Gary Speed injured, Kerr will get the opportunity to play in his favourite defensive central midfield role where he has performed outstandingly for Scotland Under-21s this season.