The contracts of AJ Styles, Shinsuke Nakamura, Karl Anderson, and Luke Gallows all expire in January.
I don't think AJ Styles would leave at this point; he's getting paid big, winning world titles, and he doesn't want all that travel.
I could definitely see Nakamura leaving, though. His WWE run has been underwhelming and NJPW is said to be very interested in bringing him back.
Karl Anderson is the one hurt most by WWE's restricted in ring style and especially their scripted, TVPG promos. I don't know if he wants to leave or not but he's definitely the biggest example of WWE making someone visibly worse.
Gallows is whatever. He'll probably go where Anderson goes.
AJ will stay because he said before he signed with WWE that he was on the last leg of his wrestling career and wanted to retire with WWE.
The other three will be offered just enough money to keep them from showing up at the MSG show next year.
Shinsuke Nakamura well know enough now to have a major IWGP title run to boost the company world wide.
If Karl Anderson, and Luke Gallows got loose it would just be the second coming of the Bullet Club as most fans missed their first run. The true OG bullet club would be back.