Everything is based on BTC. But who knows what it comes in future. Goverment doesn't like it, and pair are not gonna be only with btc, but with other coins. But I'm not sure if there will be added inseder transfer made with btc.
I think Btc still be the top
Yes, all altcoins are based on Bitcoin. Bitcoin is a litmus paper of the market. When BTC is growing very fast, altcoins are growing as well. When BTC is falling, the other coins are decreasing in their price.