The quorum definitively helps. If too few keys/people are remaining, there are two options: download and install an updated opam (with a new set of keys) out of

The quorum definitively helps. If too few keys/people are remaining, there are two options: download and install an updated opam (with a new set of keys) out of band OR using another opam-repository (with e.g. trust-on-first-use) for an update of opam itself (which then ships new keys for the main opam repository).