I think bitcoin will be like "the online coin", it can be the unitary coin of the internet and everyone will buy and sell services or products with this coin.
USD and EUR will be the major coins on the "real" or "physical" world, but bitcoin will have the monopoly of the internet world.
It depends, there have been online currencies before bitcoin that failed. They were not based on a blockchain of PoW though. But the point is if bitcoin doesn't keep innovating it will die just as they did and become a distant memory in the online world.
And we do hope that won't happen to bitcoin, we are here for a reason right? And this forum was created most likely because of bitcoin. Hopefully though in the near future it will be as what psmachado said "the online coin" or like an online currency wherein you can buy anything online. Bitcoin still has a bright future and I'm sure the developers are finding a way for it to be more of use for everyone.