I dont think bitcoin will kill off all other ALT coins. Imagine 5 or 10 years from now end users are selling their products online and accept multiple forms of payment BTC, ETH, LTE, etc. Why not??? Just look at this chart here.
http://coinmarketcap.com/charts/#btc-percentageThis is the total percentage of the market that Bitcoin dominates. And since the beginning you can see that the peaks are becoming less and less. So this means ALTs are taking up a bigger percentage of the total Crypto market cap.
I think BITCOIN will be a STRONG crypto. It will be the mother of all cryptos, people will buy it to branch into other ALTs if need be.
Right now bitcoin is dominating the market of cryptocurrency. But altcoin aren't designed to compete their mother. For me, altcoin like ETH, DOGE, and the others are the ways to safe my bitcoin into other forms. Also altcoin are used for daily traders to earn profit. They buy it and sell it everyday, so I don't think altcoin can have same market cap with bitcoin which is bought and held for long term. Maybe in 5 or 10 years from now, we will see a new cryptocoin which is a mother of some altcoin and designed to be a rival of bitcoin, also has bigger market cap.