The Rock’s dance card is pretty full at this point and even if the script was ready he wouldn’t even begin to start shooting San Andreas 2 until sometime in the middle of next year, following the news that his video game movie Rampage has been given a 2018 release date.
San Andreas 2 doesn’t have a date at this point, it will have to come later.
At this point, we don’t even know which of these two films we’re likely to see first.
Since we have not seen San Andreas 2 yet we have little to go on as far as what a script from Neil Widener and Gavin James will look like.