Many drugs are illegal, slavery, child prostitution, kiddie porn and hired hitmen.
Yet, you can find all of it pretty easily.
So the more any government tries to make anything illegal, the more people will use it underground.
As long as the net functions and as long as 2 people see value in bitcoin it will exist to some degree.
Will it be worth 400 or more USD?
How knows, but it is still in its infancy as far as a currency goes.
Personally I think it goes up ten fold in the next month to 24 months, it could pop based on all the stuff I'm hearing about bitcoin myself, it has quite the buzz.