I'm almost 95% positive looking at the offseason I just went through in my file that the coaches will stay at Level 27.
I say 95% because in two instances of coaching changes this offseason, but former head coaches who became coordinators and then regain head coaching jobs - or level 27/28 (the jump to 28 comes from the points earn during recruiting week and players drafted). But another coach earlier in my file: Mark Dantonio, is already at Level 45. He was Michigan State's head coach, was fired after Season 1 and became Ohio State's defensive coordinator. Then next year he became Missouri's head coach and has been there since. I can't imagine in three seasons he jumped from 27 to 45 on slow progression.
EDIT: The definite answer is they retain their level. In my file, Jim Grobe (former Wake Forest head coach) and Jerry Kill (former Minnesota head coach) are coordinators at Missouri. Each has their coordinator level maxed at 27, but the game says they are levels 33 and 31 respectively.