I don't think many people would flock to bitcoin even if the US dollar was in trouble. It needs to be a readily acceptable method for payment for it to be treated like a legitimate alternative to the dollar, and it's not that way yet.
If the dollar collapses, people usually go towards physical assets and in particular, precious metals and real estate.
but many will go to bitcoin in this case, and will increase the adoption which will start a series of events that will increase even further the adoption, so the collapsing of the dollar is for sure beneficial for bitcoin
For that "many" to go to Bitcoin they need to know how to use it and be sure about it, which that is still only a small member of geeks compared to the mass of average joe and the rest of the sheeple, if this wasnt' the case Bitcoin usage would be sky rocketing in Greece as we speak, but people is too clueless yet.
Yeah, it basically needs to be as easy to use as a debit card and almost as widely accepted. Anything more complicated than that won't get the entire mainstream crowd. Then the unit of value needs to be understood for pricing. Most people have trouble converting currencies in their head to understand pricing, and bitcoin is definitely more difficult as it goes into decimal places.