Your argument is incorrect. People choose their medium of exchange based on transaction costs, not on “backing”. And the transaction costs are almost always determined by liquidity. This is why gold cannot compete with fiat unless fiat collapses, irrespective of government interference. Kindly consult Rothbard’s The Case for Genuine Gold Dollar, http://mises.org/rothbard/genuine.asp. Rothbard makes it clear that abolishing legal tender laws is insufficient and people would still continue to use fiat dollar. He does not use the term liquidity, but other economic schools do.
Bitcoin presents a revolution in technological aspect of transaction costs which cannot be matched either by fiat nor by what has been commonly understood as commodity money. Market actors that are sensitive to transaction costs, or that whatever reason suffer from high transaction costs with fiat are motivated to switch to Bitcoin.
Depending on where you are, Bitcoin already has higher liquidity than many forms of fiat. The example I like to use is when I came back to Dublin last year from the Bitcoin conference in Prague, and the exchange shop at the airport refused to take the Czech crown coins I had, because they only take notes. So I’m stuck with Czech crown coins that I cannot use unless I go to the Czech Republic in the future, or find someone in my proximity who goes there and is willing to trade it against euros (or Bitcoin). But Bitcoins are form-invariant. If I want to sell them, I just need to transform them into a digital form and anytime from any location transfer them at a negligible cost into an exchange and putting an order. That gives me digital euros or usd which I can then use for spending.
Bitcoin does not necessarily have to survive, but the reason for its doom will not be a lack of backing. It is actually the exact opposite, adding backing to Bitcoin would mean its end. It would make it into a wannabe money substitute. This would both increase their transaction costs, as well as eliminate the purpose of the exchanges (as there would be no floating exchange rate). The demand for Bitcoin would become a derivative of a demand for whatever the backing was, rather than a demand for a medium of exchange, which would screw up with the remaining markets. No exchanges and screwed up markets result in no liquidity and the whole thing would collapse.