Bitcoin has the first mover advantage, but that doesn't mean it is guaranteed a seat at the head of the pack forever.  Other crypto-currencies have a chance to succeed alongside bitcoin.  Success isn't necessarily driven by being the most expensive coin.  Adoption is a necessary hurdle that even bitcoin can still make large strides in.  I could see certain countries naming official digital currencies that are not bitcoin, to try to bypass any scaling issues that bitcoin has faced.  That being said, any new crypto-currency will need to show some unique value that proves it is not just another BTC clone.