Never say never. Bitcoin is for now in great shape - it is considered as the best investment of recent years, but no one knows how it will scale.
Gold has a long history, it was always regarded as something precious and valuable for every single nation - there is no country in the world where gold is not appreciated.
Bitcoin from the other hand can be either very successful or in the long run fail to capture people's attention and fail.
Although everything is possible, but still i will like to say that bitcoin is the mother of all currencies and not a single currency has the potential to take its place. I think in present time we cannot expect that bitcoin gold will take bitcoin place. I am sure bitcoin will remain as number one currency of the world for a long long time.
I think not because bitcoin achieved its value now with the help of miners from all around the globe. And as a miner it is really hard to make another tech for another altcoin to mine. If the miners of btc gold will achieve the same number as btc miners, then that could be the only way for btg or any other altcoin to reach the price of bitcoin today. Because investing alone is not enough for an altcoin to go up.