Nonsense. if someone hacks SHA256 and mines all the remaining BTC in a day, the value will plummet and the scrypt coins will take over.
Oh dear.
You do realise all altcoins still use SHA256 don't you?
Scrypt is only used in block generation. The addresses are still calculated in part using SHA256 to convert the ECDSA public key to the addresses you and I see.
Oh dear
You do realize I was talking about block generation!
How about something easier for you to understand.
Say someone invents a new super ASIC that's thousands of times faster then the best ones currently on offer. They set up a farm, grab 99% of the net hash rate, attack the block chain a bit, let the difficulty rise to a hundred times higher than it was, then switch the farm off. Bitcoin is stuck at a crazy high diff and effectively ruined, transactions grind to a halt, game over.