"But in this post cataclysm world, what do we do about long term archiving? Stuff we actually want off-line? Or are we supposed to change our way of thinking and eliminate the concept of off-line storage altogether? (Please no...)"
In terms of archival-class storage, tape still wins. Its physical properties are better suited for the job than any other medium on the market to date. Thing is, it's become so niche that it's basically an enterprise-only solution now. In contrast to the late 90's when it least had a prosumer solution which I miss terribly; I would LOVE to have something that can keep terabytes of data safe in cold storage for about 5 years plus (basically long enough that it maintains its integrity until it's replaced with the next evolution). Hard drives are rather iffy at that length of time, and everything else is too small, not reliable enough, or both.