Mmm... If you had a kilo of gold, would you really exchange it for bitcoins?
The only people who push for that is those who have bitcoins--possibly acquired when it was worth nothing. If I had gold I would keep the gold, not replace it with something that might be worth absolutely nothing overnight.
What makes you so sure that you won't wake up one day and find out that someone managed to synthesize gold, or found a gigantic cache of it somewhere? I wouldn't be so sure about the chances of that happening being lower than that of sha256 being broken.
Gold can alredy be synthethised, but either all synthetic gold isotopes are radioactive or you have to use very rare metals (like Pt or Hg196) to obtain stable Au197. To do that you need a particle accelerator or a nuclear reactor, both of which are very expensive.
The solid gold asteroid crashing onto Eatrh theory is even less plausible. So I'd venture to say gold is a quite safe store of value for the time being. A lot better than Bitcoin or any other crypto currency that could be easily wiped out in the event of a nuclear blast or rendered useless in the absence of electricity.
Gold is valuable because of its chemical properties and as long as there is a demand for high tech electronics and jewellery it will continue to be so.
