What are the chances Ethereum will surpass Bitcoin by market cap?
Will not happen. Bitcoin will be the number one forever in the cryptocurrency. As you can see without bitcoin there will be no alt coin. Bitcoin is the pillar and king of Cryptocurrency thus no one can shake its position as the number one.
But blockchain is not about the kings. It's completely opposite - about de-centralizing. A lot of people moved to BitcoinCash already. Again, main parameter - usage, ETH is far ahead for some time now, and that is adding value with every day.