Looking at the hidden wiki, I counted 13 - that's thirteen - sites similar to Silk Road on Tor, some of which also accepted Bitcoin. I didn't look deeply into all of them, though. This does indicate, however, that this isn't going away.
It's not going to go away, from a numbers perspective, it will become infeasable for the state to prevent this sort of activity on a large scale.
Think of the effort it takes to shutdown a single site like SR, or catch a single seller, it's a huge amount of work that requires a lot of expensively tallented people to do. And that's just to catch one person or shut down one site.
Now multiply it a thousand times (probably more), now the resources needed by the state become absolutely stupendous. They are faced with the choice:
1) Give up, it's like drilling water.
2) Continue despite it's massive waste of resources and almost total lack of effect.
3) Pour army size resources into combating this issue, while at the same time curtailing peoples rights
The state can't afford 3, and they won't give up (I don't think they will) so 1 is off the plate, leaving 2.
The easiest targest will become the customers, so it will be individual users, buyers that will be the first arrested.
Also I was wondering how illegal is SR? They don't actually sell drugs themselves, they are simply an intermediary, matching up traders. SR themselves aren't doing anything illegal AFAIK (please tell me otherwise).