But in that hypothetic scenario I don't think bitcoin would monopolize all the available capital of the world. I have no doubt that most people would prefer to diversify risks through investing in other altcoins, metals or different assets, taking into account that fiat money would not exist in that scenario.
In hypothetical discussion everything is possible. This is just creating a scenario to see thing if it fits. I also agree that Bitcoin do fit in a role as major currency but I guess it will be best if it is an alternative currency next to USD or other major currency in the world. Bitcoin as we know is only a program that can be upgraded, modify or downgraded depends on the needs of the situation. So whenever math says no, the dev can interfere as "divine intervention" to make math agree with the current scenario.