JDJ signed a new deal in early 2019, as did ZZ. However the lengths of the deals were not confirmed by the club. JdJ seems very settled in the UK, however his mate Gaby may be in his ear that French D2 is a good place to be. There is very little ZZ social media activity so that is much harder to call.
If were to guess, on some of the other unanswered questions I would go with;
Carr - will stay, this is a 'must do' deal IMO, he does seem settled in the UK/Coventry and is a standout performer
Sopoaga - will stay
Morris - will stay
T Willis - will stay
Shields - will stay, still in contract I believe for one more year and then more than likley team up with Chris Boyd again at Saints
Matthews - will leave, take the French payday
Johnson - will stay and hopefully become part of the coaching set up, sadly his playing options are limited as we are so strong in the back row and at hooker