The world will be an interesting place, for sure, if we can find discover a way to create elements from nuclear reactions of other materials.  Frankly, I don't think it will happen.  If it does, it changes what the definition of an element is.

As for gold backing, the real issue at play here is what the free market accepts as money.  Gold has been accepted as money for several reasons: lack of usage in other applications, predictable supply increases, labor required to obtain it, divisibility and other physical properties, etc.  However, the real value in gold is simply that its acceptance is universal.

Money has many 4 properties.  Two of them are particularly important.  One is that money is a store of value (hence the required labor factor).  If it doesn't store value, it's just a currency - a legal tender - likely in existence only because of the monopoly of power that the state has.  The other property is general acceptance as a medium of exchange - something that the state can make happen through force.

Gold has always been the currency of last resort because when all else fails, the market chooses gold because it has *both* properties.  Governments have little desire to create money that has a real store of value because it disables the political class' ability to buy votes.

The sheer fact that bitcoins use energy for creation and that supply (at least rate of growth of supply) is limited and cannot be changed based on some central authority qualifies it to compete with gold and other monetary instruments.  This, of course, has a few risks.  The obvious one is that it's a natural enemy of politicians everywhere as it removes their mechanisms of control, but then again, that's a bitcoin's biggest advantage over gold.  Remember, gold is generally accepted as a monetary instrument - that's tradition.  Governments generally seek to disable that strength through tactics like confiscation and other abuses of the monopoly on force.  But from a market standpoint, this makes bitcoins more attractive than gold.  The decentralization aspect is the only reason that any serious attention should be paid to bitcoins.  Otherwise, it has all of the risks of gold - so why not own gold with a longer track record?

Bitcoins have earned the right to compete in the market place.  The timing is right.  We'll see how the market accepts them in time.  Forget a movement to back them with something - that's just eliminating their true value proposition.