Well i think for the Marketcap who will pass the Bitcoin, it could be XRP. Why not ETH because the movement about marketcap ETH was really slowly. Sometimes XRP can beat the position 2 of ETH.
Currently marketcap of XRP is bigger than ETH's marketcap. I can't imagine the possibility of beating bitcoin with any alternative coin. XRP is centralized but i accept the fact that big banks should start from some point no matter which crypto they prefer.