I don't see any big threat that can bring bitcoin down, the hardfork happened and yet after few moments bitcoin stand tall again without dropping from the throne, the government wont be able to stop all of the users and the users always got a way to support bitcoin, world war maybe can bring down bitcoin but not all country is joining the war and the chances to happened is low
Chances would really be slim which we are really pressumed that this thing is somehow impossible to happen.Bitcoin wont easily die as long the community do support it, no matter how government would ban it there would be still supporters of it which it cant really easily for bitcoin to die.Biggest threats? I cant see one but the thing here would be involved is mainly on our government but doesnt matter at all because bitcoin would remain still.