The economic reach of Bitcoin is an interesting subject of discussion. In the end there will be a maximum of 21.000.000 BTC. BTC is a eight-digit number.
I suppose that a currency can only be leading if it has the possibility ta pay in small amounts, equivalent tot e.g. dollarcent or eurocent. This statement limits the range of BTC, will the satoshi be the future euro/dollarcent?
In that case the maximum money supply wil be BTC 21.000.000,00000000 is e.g. EUR 99.999.999.999.999,99 (by the way: interesting exchange rate).
The money supply in the Eurozone (M3) is over EUR 10.000.000.000.000
So without any constraints, the structure of the BTC satisfies the necessary condition.
Let's inventory the other constraints.
Have you heard of mBTC, bits and satoshi?
There are 10 millions satoshi in a bitcoin.
That's pretty much enough for now on.
And if it would really pose a problem a hardfork would solve it but again it is not necessary.