Dark Phoenix is already a stinker with Kinberg the only one writing it. And unlike his previous X-Men scripts, there's a possibility that he will direct the film so there won't be a person to course correct his shortcoming with the script. So yikes. I also don't see why Kinberg would stop writing especially if he's also producing and directing the film. The strike could last for years, and he'd be done with the script by October.
The other two won't be affected. I don't see any of these three films being affected by the strike. If they get a new release date , it would be for other reasons like late start of filming which is kinda the case as of the moment with New Mutants.