Maybe I understand this completely wrong but moving the decimal point doesn't change the real value of the coins.
If I have 10 btc and it's worth 10usd and the next day those 10bct become 100btc I still have 10 usd worth. So they're not deflated or inflated.
This isn't creating coins.
If in this example we move the point one digit right the number of coins increases 10x but the value stays the same.
If the current 1btc rises too high it's not going to make sense to trade 100usd for .01 btc so they move the decimal point.
Inflation on the other hand would be creating more coins (which is happening but levels off).
Forget decimal points and all the rest of it. Think of the more people joining the system as population growth. Now the same amount of money has to feed clothe and sustain more and more people but, we only have a fixed amount of money 21 million bitcoins (remember the original sentence said that bitcoins is a major world currency). Think of it in the real world where you live, no more credit, no more real money, than there is at this very moment but, the population got bigger and bigger over time. that means there is less money to go round but it has to buy the same amount of basic goods and services that we all use. these basic goods and services would need to be dropping in price over time the opposite of what happens in real life today. bit coins can work with one change and that is not to limit the amount of currency that can be produced but, to match it to the goods and services that it needs to be used for (not for speculation and not paying interest with money that does not exist).