I don't see ETH surpassing BTC.  ETH has its own fair share of flaws and limitations.  The crypto space is evolving, and expanding so quickly that by the time BTC is passed up (if it ever will be) ETH will be just as ancient.  There will always be something newer and brighter coming down the line.  That being said people do gather around what they know, and BTC has the greatest/strongest reach for name recognition.  If mass adoption is the goal BTC will be the rabbit hole...... of course that is all based on the current environment..... who knows what tech is about to be developed.......