Great post!
I think the chance that Bitcoin is overtaken is smaller than most people think. The technology is actually only a small part of why Bitcoin has it's value. The real value for Bitcoin comes from the security of the network (which is secured by the high token value and hashpower making it super expensive to attack), and the network effect of Bitcoin. By the last part I mean: the community, amount of service providers, development and adoption.

The network effect is probably the largest factor actually. No other competitor has the kind of network effect that Bitcoin has. Especially the newer altcoins have a laughably small community compared to the Bitcoin community. Even Ethereum, big as it may be, has a much smaller network effect and is pretty much only popular among crypto-enthusiasts. The mainstream is not even aware of something like Ethereum, let alone Bitcoin Gold.

This is also why I am doubtful that newer competitors like RaiBlocks really stand a chance. Yes it's perhaps vastly superior to Bitcoin for peer to peer payments... but who is using it except a few handful of speculators and enthusiasts? It took 9 years for Bitcoin to gain the network it has now, something like Raiblocks would be hard pressed to catch up to that level in time.

I'm of the opinion that a faster blockchain doesn't matter either. What it comes down to, is the fact it's decentralized. How quickly or how often you 'save' to the blockchain is really irrelevant, as long as it's trustworthy. I think Lightning network, which 'bundles' transactions and periodically updates the main chain, will probably create a situation where transactions are free or nearly free. On that note: Bitcoin transaction fees are currently down to mere cents per transaction.

I myself am wondering if there is any reason for many altcoins to survive, if Bitcoin fixes the scaling issues. I think Bitcoin Gold has more to fear from Bitcoin than the other way around.