Sitake can replicate Bronco's success. Because with the more challenging schedules coming up that is a real question.
Alot of Cougarboarders like to blame Bronco for the program "slipping" since 2010 -- as if averaging more than 8 wins a season for 5 years straight is "slipping" -- but the two main reasons for the drop in on-field results is playing 2-3 more P5 teams every season, as opposed to playing 2-3 G5 patsies, and getting out-recruited by Utah. And the drop in recruiting was more due to lack of P5 status than anything Bronco did.
BYU has never played more than .500 ball against "big boy" teams, not even in Lavell's era. And Lavell's winning percentage (0.717) and Bronco's winning percentage (0.697) are very close, which tells me that Sitake will be hard-pressed to win more than 70% of his games during his career, let alone go undefeated.