Nothing at all unusual, nothing even implying an "exodus" in the typical understanding of that word.
To wit: according to the two following sources, this is what "exodus" means. Dictionary.com = mass departure of people: Meriam Webster = mass departure. Sure, we can dither over what exodus means but in the most common use of the word, this isn't remotely an exodus.
And BVZ's point stands. At this time of year, there are significant changes in coaching personal staffs.
By the way, which "Brown" on ND's staff is leaving?