Bitcoin have every feature required to be a World Currency, but every country won't take the similar stand. For now few countries have shown green flag and one have made it legal tender within the country. These are part of development. Bitcoin will serve as the alternate to fiat, because it is really tough task to eliminate the entire usage of fiat and implement crypto.
It is tough at the moment, but with the growth of adoption technical part of bitcoin core will develop as well. Main problems are known and there are many different decisions of their salvation: now we look if some of these decisions can be useful while they are being tested on altcoins. I'm sure some ideas will be found when needed, we just need to wait a bit.