I know a bunch of people already responded but I figured i'd condense it all into one post in case you still don't fully understand.
So based on your original post (on 12/4), I'm assuming when you say “earlier today” you mean 12/4. With that being said, you should receive your score on 12/19 at 12am (unless NASBA starts releasing them a few hours early).
Now if it's the worst case scenario, and you find out you failed REG, you can retake it but will have to wait until the next testing window which would start January 1, 2019. As a result, you would have to take the exam based on the new changes. Since one of your other sections expire in January, my recommendation is to prepare for the worst case scenario and get a new study book with the new material and start studying NOW (I know if you have Becker you can start studying the new tax law).
Again worst case scenario, if you fail REG, you will be good as long as you take REG before your other exam expires (as long as you pass REG).
So for example, lets say your FAR exam expires January 15th. As long as you retake REG sometime between Jan. 1- Jan. 14 and pass, you won't lose credit. Even if you wont find out your score for the REG retake until Feb. 5th.
BLACKOUT MONTHS: To answer someone elses question, the year is broken down into 4 “testing windows.”
Each testing window includes 2 full months, and then the first 10 days of the 3rd month. You can only take exams during these windows: So basically testing windows are as follows (and you wouldn't be able to take an exam on March 20th for example).
Jan 1 – March 10.
April 1 – June 10
July 1 – Sept. 10
October 1 – Dec. 10.
Lastly, if you fail an exam, you cannot retake it until the next window.
So for example, If I study for REG and take it on January 15th, then find out on Feb 5th (score release date) that I failed, the earliest I would be able to retake the exam is April 1.
If anyone is curious about the 2019 score release dates, here's the linK: https://www.aicpa.org/becomeacpa/cpaexam/psychometricsandscoring/test-windows-score-release.html