It is thus absurd to compare bitcoin to gold, yet. In 2000 years, if it's still around, I'm happy to accept the comparison.
I can find you people today that would take a gold coin for their services instead of a bitcoin (obviously worth far more), because they don't care / understand / trust it. The only reason I can think gold would no longer be valuable would also nullify the value of bitcoin - the demise of capitalism or anything like it, and the advent of a currencyless society.
No it's not going to work because gold is very scarce and extremely valuable as a material in any case.
Yes, the price would take a hit, likely something between silver and current gold price, which would increase use and demand and then price again.
There's a reason we're thinking of mining it from asteroids.