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.
I would not go that far but see your point, the majority of alts are either weak projects, just have products on paper or are scams that only indend to grab money. But among them you have also pearls that can disrupt entire businesses if not markets.