When announcing its official roster of 124 officials for 2016, the NFL specifically pointed out that all 17 referees will return. Although the announcement also names three new officials who will be joining the overall workforce for the coming year, there was no mention of anyone who won’t be back.
With 122 officials last year and 124 last year, the addition of three new officials means that one is leaving (#math). Per a source with knowledge of the situation, head linesman George Hayward has retired.
The league doesn’t provide details as to why a given official has left. That’s a product of the push-and-pull between the league and the NFL Referees Association, which as part of its duty to represent the interests of all officials tries to minimize or eliminate any public embarrassment of them — except when the executive director of the union decides to call them out publicly for decisions made or not made during a given game.