Look at the history of currencies.
The British pound sterling, the French franc, the Dutch guilder, they all were reserve currencies but they got overtaken.
Usually not because their inherent values changed but because the environment changed and another, more suitable currency emerged. That's exactly the narrative that people push about Bitcoin's advantages over the US dollar.
But because things happen a lot faster in crypto than they do in traditional finance, I wouldn't bet on "Bitcoin can't ever be overtaken".
Think about it… it's highly unlikely that something else could achieve the network effects, mindshare, hashing power and all of the rest of bitcoin's attributes right now. In the early days, when bitcoin barely had any value at all, it would have been possible. But having gone from $0 to $350+ billion in market cap, it's too late.
Quoting Travis Kling (@Travis_Kling):
"Bitcoin is a non-sovereign, hard-capped supply, global, immutable, decentralized digital store of value. It’s an insurance policy against monetary and fiscal policy irresponsibility from central banks and governments globally."
This explains why Bitcoin won't be overtaken.