aye, the one thing bitcoin has going for it there is that we are able to bump the new priv keys up to 512bit, 1024bit, etc etc. This would require anyone with coins still sitting in an old 256bit addy to move them to a new one to get that security though.
The lost bitcoins would be sitting in addresses which would not have been "upgraded".
It might be possible we take advantage of this vulnerability to recover "lost" bitcoins. If ASICs in the future are in the range of $/TH and the block reward is low enough, it might make sense for miners to attempt to "crack" these vulnerable addresses and release the stagnant coins instead of mining new coins.
You would hope if the old address, even if cold storage had real owners any more they would be still keeping up on Bitcoins and if smart would not only move their cold storage BTC to a new regular addy periodicly to help avoid that but would surely get their ass in gear to move to new 512bit addy asap if it was implemented because of the potential for new tech to greatly reduce the collision time.
because I highly doubt this will happen. 
