I just chatted with a Samsung expert, and they advised me that the beta is full and to wait for the stable upgrade. They said the stable (official) upgrade will be pushed to our phones between January and March 2020. Hope this helps! I've been trying to sign up for the beta for months but wasn't able to. I have a Galaxy S9 Plus.
Only people with the FACTORY unlocked version could get the beta update. Carrier unlocked is not the same as factory unlocked. If your model number is, for example, SM-G965U, you are not factory unlocked. SM-G965U1 is factory unlocked. Note the number "1" at the end of the model number.