It is certainly global if you mean it can be transferred anywhere with ease, however.
Thats reasonable, Bitcoin is really currency without borders and not controlled by any country - pretty much ideal in global trade. But Bitcoin cannot replace USD and other currencies because with maximum 5 transactions per seconds, it is not enought, even if you increase 1000x the thoroughput (1GB blocks

), it is not enought for replacing all other currencies
I doubt that bitcoin user base will be that large so we would need capacity that huge. Not right now, and probably not in the near future. Bitcoin community as of now is maybe 4-5 mln people, at most!
Until we will need more transactions per second, considering our growth, it could take years. Until then bitcoin core protocol can be changed to answer these problems.