Moving to crypto or gold after it falls is much too late as your holdings would lose its value, but that's up to you. I can't say what would be used in such a case, but if countries with failing currencies are an example, they moved to buying USD, Bitcoin etc. Ultimately, you move to the best alternative and in the case of fiat, BTC imo is the one but who knows. I don't think you can just create a new blockchain and expect it to all work out after the fact :)
I would still say based on the practicality if you look at any cryptocurrency it would falter under the load of transactions as large as the whole US for example. So it's a bit early to bet the farm on any one of them. Also if a govt will support cryptocurrency they will create their own one so they can profit off their own ponzi, so to speak. They wouldn't be in favor of enriching Bitcoin whales just to take advantage of the 1s and 0s previously established in the btc Blockchain
Lightning network on Bitcoin already supports a higher throughput than visa
I don't argue that blockchain tech will keep improving. I just say if it's going to be a currency of the future why do we have to spend money on it now? Won't we be able to create parallel blockchains to increase token supply? It's not an intrinsically valued asset, like buying a stock (which some have returned more money than speculative bitcoin purchasing). Why should the bitcoin believers tell everybody to buy it if there's nobody accepting it for payments?
Re: parallel Blockchain- there are thousands of Bitcoin copycats since 2011. They're either dead or dying. See the top ten list on coinmarketcap over time. Point is that value will accumulate on what everybody agrees on and there's no way somebody's CrapCoin where they own 60% of tokens and dump it on the market will gain traction with it's inherent risks (security, centralization, lack of differentiation etc).
Bitcoiners themselves don't spend using Bitcoin yet but this change is happening as more and more people believe in it as something that holds value and isn't going to 0. It'll take time and I have patience.