It is a monumentally bad idea
to retain revoked key material - especially when you don't
actually have any way to use it.
My concern is that we don't know if we have any way to use it until KSK rollovers stop being science projects.
The topic that prompted the concern was Warren raising Wouter's old trust anchor link proposal from the dead. I thought Wouter's proposal was a bad idea, years ago and I'm not sure whether Warren's current idea is best described as a recurring bad dream or a prodigal son returning, but it seems silly to rush to a conclusion when we don't need to.
What is the harm from keeping leaving the KSK-2010 smart cards that are already in the safe there for as long as it takes to have a stable plan in place for rolling the key? This is not a rhetorical question -- you know more about this stuff than I do, and I'm interested in your answer.
Note that I'm not suggesting that old key materials be hoarded as a general principle; rather that since we don't yet know what we are doing, perhaps we shouldn't act as though we do.
Joe