never say never!
of course with price and with usability and real adoption, ethereum can never surpass bitcoin's marketcap but ethereum is not known to be an honest coins and market cap is a useless number that can easily be manipulated!

for all we know Vitalik is going to fork ethereum another time in the near future and change the available supply from current 90 million to 400 million and easily surpass bitcoin's marketcap.
it is a very simple math 400,000,000 * $47 = $18,800,000,000 marketcap > bitcoin's $18,518,449,188 and when ETH price was dumped back down to $10 he can fork it again and increase the 400 million to 10,000 million