I am sure countries will want to censor it, but I don't believe they will be able to, as such the only risk to bitcoins long term viability is the markets demand. There are numerous examples of illicit goods that governments have proven incapable of reducing the demand for, e.g. drugs. So I don't think bitcoin is going anywhere.
I think bitcoin will take a different censorable form and we'll start seeing companies on top of the blockchain that can do things like refund unauthorized transactions and things of that nature, but the base layer will remain uncensorable and thus bitcoin could become both convenient enough (although not better, in my opinion) for rich countries to use as currency while holding the characteristic of providing tremendous benefits to citizens in oppressed poor countries.