No, see, you are missing some steps. Bitcoin won't "become the sole reserve currency" with the current distribution. The Federal Reserve, the ECB and the PBOC aren't going to put out press releases saying "We've adopted bitcoin as the reserve currency. We don't have any. Can you sell us some?"
The banks need to acquire them first. That means buying them from people. That means changing the bitcoin distribution. In particular, the central banks would need to gather many, many bitcoins before they could consider using it as a reserve.
Your analysis is very static. You don't see the system as being a living, moving thing. But I figure your post is much more political than it is analytical.
If the banks had to buy them from people, you think they would buy them at whatever the speculative (out of thin air) value is? They would run it to the ground before they would 'buy' a single coin, and at that point it would be useless. The government and/or media can destroy Bitcoin at any time. They've never redistributed their wealth and they're not going to start now because of cryptos-- nothing will force them into that situation, they are the ones in charge and there is no way in hell they will allow competition-- for them, everything is at stake.
This is why I mentioned Bitcoins simply disappearing. My question is a hypothetical/philosophical one.
Most people with some ideals see Bitcoin as a way for the banks/govt to stay out of our pockets-- to not allow them to take more than they already have-- this is seen as unjust. Bitcoin is seen as revolutionary by these people because of its ability to accomplish this. I happen to think that these same people acquiring so much of something for pretty much next to nothing, is also inherently unfair to those that don't, and won't do anything to redistribute the wealth from the ultra rich to the ultra poor. It is a potential revolution for the 'haves' in denial but not for the 'have nots'. They will not actually be taking anything from the super rich, and the wealth (because of the very nature of 'wealth') has to come from somewhere or be in relation to something else. That relation will only cause the poor to become poorer because they didn't gain anything of value, even if they didn't actually 'lose' anything.