There was a very good post during training camp pointing out that the transition to 3-4 often takes a few years to complete, and that quite often a hybrid is used until all the pieces are in place. This is whats going on right now.
Gailey said he likes the 3-4 because a) it's what we face in division games, making it a bonus to practice against, and b) because as an offensive guy, he feels it's harder to prepare for.
Expect us to stay hybrid next year again with maybe a bit more 3-4 as the guys become more accustomed and or suited to it.