Currency failure generally occurs due to the type of hyperinflation, and there is always the potential for technical failure, currency competition, political issues and so on. As the main basic rule, there is no currency that can be considered very safe from failure and difficult times. so is it possible that bitcoin can become worthless?
Yes, that is possible! But I don't think it will happen anytime soon.
I think the opposite is about to happen, bitcoins will slowly become the safe haven, do to the endless Quantitative easing from all the worlds central banks.
Owning gold, land and now also bitcoins will most likely grant you financial freedom, next time we see a market meltdown.