Which Bill of Rights amendment would most likely be used for expansion or addition of future rights?

The Ninth Amendment would most likely be used for the expansion or addition of future rights. The Ninth Amendment states that the enumeration of certain rights in the Constitution shall not be construed to deny or disparage others retained by the people. Essentially, this means that just because a right is not explicitly mentioned in the Constitution does not mean that it does not exist. It allows for the recognition of new rights that may emerge in the future as society evolves and progresses.