That would be an ideal time for someone to launch a competing coin. I figure it would take <$1 Billion to overcome Bitcoin's first mover advantage and then the banksters will just keep running the world as if we never existed.
Well, bitcoin is not to be used for ordinary e-commerce payments, its first move advantage is not worth much.
Litecoin and Dogecoin are already there. WIth some PR and a couple of legal exchanges in the US and Europe, Litecoin or some other new coin could take over many uses of bitcoin, if it offered faster service and/or lower fees. That would cost a few M$, but much less than 1 G$. Bitcoin's recurrent traffic jams at peak hours would be the best marketing, for free.