More than Bitcoin as Money?

In the future, it may be that all currencies are converted to one common money. So instead of carrying around change in your wallet for every purchase you make and handing over cash at a checkout counter or exchanging money with somebody who has another form - like dollars vs pounds- we'd just use crypto coins as payment everywhere!
The big debate continues between those two alternatives: 1) Will there only exist ONE dominant monetary store (Bitcoin)? Or will more emerge in competition? 2). If so many different Cryptocurrencies coexist then which ones survive depends upon how useful they actually prove themselves out...