I'm sure, if there is no altcoin then like a man without a woman, bitcoin will die and will not get people interested. Remember, one advantage is the large number of bitcoin altcoin, but I'm sure that one day there will be a coin which replaced the bitcoin.
there is a lot of good altcoins which gained a lot of value and user's attraction. but I don't think any new coin can replace bitcoin.
miner's won't let it happen. bitcoin is first and the only crypto currency which got that much success.