The stars of New Japan Pro Wrestling's Bullet Club had just finished wrestling at WrestleKingdom 10, the biggest wrestling event of the year for New Japan when word leaked that they were leaving for WWE. There had been no forewarning whatsoever prior to that word leaking out in the hours following the big show at the Tokyo Dome.
Since 2016, Styles has gone on to become one of the biggest stars in WWE, holding the WWE Championship on multiple occassions and becoming an overwhelming crowd favorite. WWE has recognized his value, giving him incredibly long title reigns by modern standards and running with his popularity.
On the other hand, Anderson and Gallows have not reached the levels of success in WWE that many had hoped for. The two were a fantastic tag team in New Japan, one of the best in the company, but they haven't been given as much of a chance to shine with the WWE.
Lately, there have been a lot of questions surrounding the contractual status of all three men since we are coming up on the three year anniversary of their big jump to WWE. PWInsider jumped in to clear up the confusion: Styles' contract expires in April 2019 while Anderson and Gallows are signed until September 2019.
Most of the rumors surrounding these men has been centered on whether Gallows and Anderson could be weighing a return to New Japan given their lack of on-screen success in WWE (their pocket books not withstanding). There's nothing concrete to report there, though obviously working in North America and making good money versus having to travel halfway around the world is something that will weigh on their minds when making their decision.
Some rumors had indicated that Anderson and Gallows' contracts would expire at the same time as Styles but that doesn't appear to be the case.
As of this moment, Styles is expected to stay with WWE, though he has no signed a new contract. There are some rumors that he has started negotiating with the company on a new deal that might include a clause about having to work less dates than he is currently obligated to, but there's also nothing to report there that is confirmed.