I don't see any reason that it will become illegal in a tax free land like Bahamas
The main reason BTC could be a headache for government, is because they could not collect tax on BTC transactions, and there is no way to map the account to physical person/institute
And I think central banks don't really care about it either, what they need is a currency that they can control the money supply, in this way they can affect the macro economy the way they want (price stability and low jobless rate). A currency with a fixed supply is totally useless for them from modern economy point of view, since it neither can bring price stability nor lower the jobless rate
Actually the later could be true, if BTC price increased so much that it created another bubble, it might create many jobs, mining companys, BTC exchanges, client developers, online wallet institution, same as those gold buyers recently. In that case, if it is also good for economy, and can achieve what they can not achieve with normal monetary policy, why claim it illegal?