There are two different ways that can go!
If the subscribers were added to your Sequence via a Visual Automation14, they will not receive any newly added emails. This is because Visual Automations remove subscribers from Sequences and mark them as "Completed".
For example, if they’ve already reached the end of the Sequence they will only receive new emails added to the very end of the Sequence. (They won’t receive new emails added to the middle, since they’ve already passed that point.)