Finley (and
Finlay) are extremely popular for boys in the UK right now. However, I think there is a good chance that
Finley will never become very common as a boys' name in the USA but will go right to predominantly female over here if it becomes popular. Most Americans seem to think that -ley is now a feminine suffix on given names. So I suspect that on the western side of the Atlantic,
Finn and perhaps
Phineas may become popular for boys, and that Americans will see
Finley as the feminine form of those names.