It should dominate the market and it should be more than 50% because we know that most of the altcoins just existed to squeeze more money from uneducated investors waiting for their profits that will never happen. Bitcoins should be 80% when a stricter regulation is implemented in the future.
Bitcoin will dominate the market for many years. I am absolutely sure that BTC is the cryptocurrency that does not have any rivals for now. Probably, these cryptos can appear in the nearest time - 5-7 years.