According to a report at wrestlinginc.com, originally reported at MLW Radio, 4 time WWE Intercontinental Champion, 2 time World Heavyweight Champion, 1 time WWE World Tag Team Champion, 1 time WWE United States Champion and 1 time Mr. Money in the Bank Dolph Ziggler MIGHT be leaving the company when his contract expires in a few months.
According to the report, there've been rumors of Ziggler being unhappy for quite some time. During an episode of MLW Radio, former WWE writer Court Bauer commented on the rumor, referring to Ziggler leaving like John Morrison did. Morrison now works for Lucha Underground as Johnny Mundo. Bauer said:
"Dolph's deal is up in a few months and he has indicated informally that unless he gets a big push, he may leave like Mundo."
I'd say there's probably a good possibility of this being legit. There've been other reports over the past few years of Ziggler being frustrated with not being given a substantial main event push; partially, allegedly, one reason why is concern over Ziggler's health due to suffering two concussions within about 6 months of each other and displaying symptoms of Post Concussion Syndrome via the first one he sustained after returning to action.
Ziggler turns 35 in a little over a month and he's been involved with WWE for practically his entire career. It's possible that, realistically, he figures he doesn't have a whole helluva lot of time left to be elevated to a main eventer, due to getting older and the fact that there's so much interest & buzz surrounding guys like Kevin Owens, Neville and Sami Zayn.