can you put a time on that?
Bitcoin (and the free market) really need to find some peg. Gold ETFs have served that purpose to some degree, but Bitcoin will drag gold much higher as its ad-hoc digital twin. If I were to venture a guess it would have to do with whichever country has enough gold and is willing to acquire bitcoins as well. When people start losing faith in fiat currency and bonds, they will trade gold for bitcoins.
I can think of unthinkable scenarios regarding confiscation of gold or its ownership belonging to a designated class. Bitcoin would be the only way the rest of us can be licensed to hold gold.
Most likely it will occur organically as fiat currencies fail. Both bitcoin and gold will see huge swings in the next few year, but 2019 will be when they become pegged.