[andy112]

I was primarily meaning the crypto primitives. (see http://valerieaurora.org/hash.html for a neat chart of past and present hash functions and their lifetimes.)

Migrating over to "bitcoin-B" or some other variant would be possible, but I would imagine it would be unavoidably chaotic if both currencies stay fully decentralized throughout the process, regardless of whether the primitives break outright or over time.