In the same sense that the only social networking sites that were "needed" were Friendster and Myspace.  Or the only web browsers that were "needed" were Mosaic and Internet Explorer. 

I think that it won't be long before BTC and LTC will be regarded as the first-generation crypto-currencies that blazed the trail, but the technology will move past them.  Proof-of-work designs in general may go out of fashion.