There is no Worst Case Scenario for bitcoin. Again, why fear governments? Please stop the paranoia. Best Case Scenario is bitcoin going mainstream. But we already know that. 
Well it does not really the only worst case and best case scenario. But as you have stated, when in terms of government control, they can not do it, but it may have a conspiracy in group of rich people. Capitalist are always doing what they can do in order for them to stay on top and that is the problem of today. On the other side, bitcoin will be more great than the current currency of today and that will be a very good thing. As of today the thing that will happen is the rise in the market of bitcoin.