At the Cosmic Shambles Network.
* Note added after some discussion with colleagues: The FCC document on which I think the Nature article relies says “The FCC-hh would essentially provide a comprehensive search for WIMP DM”. The word “essentially” seems important here; I take it to mean there are some, possibly rather contrived, WIMP scenarios which would still be out of reach. I think such an exclusion would still have a profound influence.
Link to FFC document: https://link.springer.com/article/10.1140/epjc/s10052-019-6904-3