That's going to have to involve sending your coins to a completely different set of HDKeys because if the curve is also broken in addition to ECDSA, then just signing all local transactions with the new signature algorithm won't be enough.
I'm pretty sure that's what Satoshi was saying in that quote - the software would automatically send all your money to the new address type we end up with. As ranochigo points out above, I don't think it is possible to leave coins on current addresses but transition to some form of "hardened ECDSA".