Because you'll be potentially implementing two new systems with a multiple new coaches.
If the staff decide to play younger more talented guys, you'll lose more games based on mistakes of inexperience.
JJ took a national championship team and went 8-4 the next year. Year 3 is when he was playing in the NC.
These are some of the reasons people have tempered expectations year 1. Year 2 should be division champ and year 3 play off bound.