It's possible that ETH is surpassing BTC's market cap sooner than we think right here - right now.
My thoughts behind that:

1^st - "Watch money flow!" Stocks, bonds, housing markets are all in a big fat ugly bubble; if the money leaves them - like it did last friday in the tech sector on a very small portion - big fat money will flow into other directions... especially into the cryptocurrency market and the long suppressed physical PM markets!

2^nd - "ETH is a much broader market!" Meaning by that: if I want to transfer big fat money very fast on low fees, ETH is much quicker and cheaper than BTC is right now! No one who is transfering big amounts is patient enough to wait more than it needs! ETH is also becoming a SOV, slow but steady! - (Store of Value; maybe even on a much higher return than BTC!)

3^rd - "China & Russia (& Brics)!" Some insiders say that they're trying to set up a cryptocurrency backed by Gold on the ETH-chain.... - wasn't Vladimir dating Vitalik lately??! Mmmmmh...

4^th - "Psychology!" If I have a clear goal and have come that far, I will make the last steps that it takes to reach my goal... - (as NADAL did today in Paris!); meaning some will try to pump ETH even further to kick BTC right in the ass.

Cheers folks, have a nice one!