The answer is unfortunately not set in stone, and will vary from not only model to model, but carrier to carrier. Updates are slowly released by the carriers as they make sure of compatibility. Because there are other channels besides Samsung it has to go through first, no set dates can be given, however, all eligible devices will have the opportunity to get it.
Any questions regarding a release date should be asked of your carrier. This applies to both locked and unlocked phones.
Q&A:
Q: My carrier's tech support said Samsung has to release it. Is this true?
A: No. Once Samsung announces it has released updates out, that means it has been sent to the carriers. Tech support for carriers pointing at Samsung do not know the true chain of release.
Q: Why is it taking so long to get the update?
A: Because your carrier has not rolled it out to your specific device yet. It is usually released in waves, and is not always consistent. They also want to put their own touches on things to ensure compatibility with their network(s), and add in their own carrier-specific apps/features.
The same applies for us. Samsung releases the update to the service providers who put those pre-installed apps that we delete 😂 then they release to the devices via OTA. It's how it's always been.
At least with unlocked(I think international versions as well) phones, they don't go through the mobile carriers first that's why usually they get updates faster than service provider ones.
