Could go as high as 80 percent, and if the bitcoin dominance really does reach 80 percent, then the price of altcoin could rise many times if many bull markets come to pass.
Bitcoin will remain dominant and will never see it behind due to its up going graph or improvement it will not come to second or third position and if you look at other crypto coins those have not enough potential and strength to compete with Bitcoin. Furthermore crypto coins other than Bitcoin will take a several years to reach at even the lowest value of Bitcoin.