Does the grandfather clause apply?
As of December 27, 2019 no information has been provided by the FDA regarding the possibility of a grandfather clause*. This means that the the federal age limit increase to 21 applies to everyone.
*A grandfather clause (or grandfather policy or grandfathering) is a provision in which an old rule continues to apply to some existing situations while a new rule will apply to all future cases. Those exempt from the new rule are said to have grandfather rights or acquired rights, or to have been grandfathered in.