Fiat currency will never face "death" as long as the government that issues it exists. About gold, it has a real life usage, so being certain of gold "death" is somehow delusional IMHO. Bitcoin may beat gold but it will not result to "death" of gold.
Maybe. But we can never tell what the future will bring. What if governments manage to amass most (if not all) of Bitcoin's supply? A centralized BTC would be no different than Fiat. Only then, government-issued currencies' death would be certain. The odds of this happening are slim, though.
As for Gold, it won't "die" but it will lose investor appeal. People will no longer consider it as a store of value, but rather a luxury item used solely for jewelry and whatnot. Bitcoin will eventually replace Gold as the world's largest and most trusted store of value. Countries from around the world are already recognizing BTC's potential, so it should only be a matter of time before this happens. With Russia on-board the crypto craze, I wonder if China and North Korea will be next?