Don't stress over whether RB is staying or going. I think that's disrespect for KS and the other staff you have at St Mary's. It's disrespect for the program they have built together. RB wouldn't take another job if he believed things were going to collapse without him. He is replaceable at St Mary's -and that's by his own design.
Only concern should be RB going to the wrong job, and not getting very much pleasure out of coaching.