When an innovation happens like blockchain (bitcoin) and other projects tend to follow a successful model so, its very difficult to imagine not having other crypto's being bitcoin on the helm.
How can you say so? If altcoins will be eliminated out of the market, bitcoin will be remaining still, and bitcoin is still a cryptocurrency, wherein, one of the characteristics of a good crpyo is its market volatility depending on the demand on it. If altcoins will going to perform in the market, bitcoins market volume will spike so hard as people will have no option to convert their currencies into. But, a world without altcoin isn't seems so possible.