if the dollar collapses, then bread, bottled water, milk and everything else would be worth more dollars.. EG $100 for something normally worth only $1.
this would then make bitcoins worth (using the same exampled multiplication) 1BTC=$100,000, whilst at the same time 1BTC= only EUR1000 due to the euro not collapsing
I think this is probably the most sensible answer, and since you won't be able to buy a loaf of bread with a rare oil painting or a bar of gold (think of the change problem) then Bitcoin will become the currency of choice.