It could be argued that gold is priced somewhat arbitrarily, based on market demand as a store of value -- exactly like BTC. However gold is a physical product and has real-world uses as an element.
With all that taken into account, will the market drive them to general parity? Like the Euro/Dollar?
Just because that gold may perform similar monetary functions when compared to bitcoin, at least from a store of value standpoint, doesn't mean that their values or market caps should necessarily be on par with each other.
That makes no sense. It's like saying that the US Dollar should be on par with the Euro, just because they are both fiat currencies.
You need to take into consideration the fact that value is solely determined by supply and demand, and that right now, demand for gold as a form of investment vehicle and safe haven asset due to its decentralised supply, and people's trust in its historical inflation hedging properties is still a lot higher on a macro level worldwide, leading to its market cap being much higher than BTC. However, I could see bitcoin taking a large share of the gold market cap in the future due to the fact that it is just so much more portable, and divisible, while retaining the same monetary integrity and decentralisation, which is what makes gold such a good long term hedge against fiat depreciation.