Will there be extras for this?
If the project is a group buy, usually there is a margin ordered for replacement parts and B-stock units. If any are left following GB conclusion and replacements, they will be placed on sale as extras.
However, this is not guaranteed whatsoever, and there are many cases where there are no extra units left. The best option is to expect no extras, but also to obtain the role for the project at my Discord server to receive a notification if they appear.
If the project is an in-stock sale, usually there are no extras.