There are many coins in the cryptocurrency ecosystem, but if we're going for something to replace Bitcoin, it would have to be Dash. It's following in Satoshi's original vision of a peer-to-peer digital cash, has better-incentivized governance to prevent the kinds of problems Bitcoin has run into today, and works much better as a streamlined payment system.

In fact, even if Bitcoin doesn't collapse, but stays the same and even continues to grow, Dash's Evolution update will likely push it to the average consumer far before any other coin. These will be interesting times to watch.