No. The feature is still a "feature-request" even though it already exists. It can't really be considered "discussion" because they are specifically asking for something.
Just mark as duplicate (if possible) of the other feature request, or flag for moderator attention and have them tag it as "Status-Completed" because the feature exists. That way, any other confused users who appear on Meta will be able to search and find the feature request that already exists.
EDIT If you're talking about stream-lining so that it does not influence the moderators or site owners who are monitoring those tags, it is still worthwhile to know that there are features that are already implemented that are too obscure to be found by some users.