Not quite sure what your source is referring to that, whether he means the "only" currency, the dominant currency, or the only cryptocurrency.
Anyway, regardless, things would be not in our control and probably we may not experience in the near future.
But for sure bitcoin will be part of that future, we are just not sure whether the only, the dominant, or the only crpyto.
But I always believe that competitors  are always healthy for any conceptual work.