While all three of the former Bullet Club members debuted around the same time, in early 2016, their deals are not expiring in early 2019 as some have speculated. PWInsider reports that Styles' WWE contract expires in April 2019 while Gallows and Anderson will see their contracts expire in September 2019. There's no word yet on WWE's plans for re-signing them but it's likely that they are already discussing a renewal with Styles.
Styles debuted with WWE at the Royal Rumble in January 2016 and has been booked as a top Superstar ever since. It's believed that he will stay with WWE. Gallows and Anderson debuted the week after WrestleMania 32 but they have had one RAW Tag Team Title reign since signing, and it barely lasted two months. They have been reduced to just another tag team on the midcard, if that.
It will be interesting to see what happens in 2019 as NJPW reportedly has interest in bringing back Gallows, Anderson and WWE United States Champion Shinsuke Nakamura, according to a report from mid-October. There was no mention of the company wanting Styles back but it's likely they would negotiate with him if he were interested in leaving WWE. The report from October stated that there was talk of Gallows being interested in returning to Japan, but it was believed that Nakamura and Anderson would stay with WWE because of their lives here in the United States, among other reasons.