I think when we talk about "replacing Bitcoin" it depends in what sense?  If we are talking store of value I don't think this will happen for a long-time for any other coin.  There is simply just so much money in Bitcoin.  It may be Ethereum as well but I personally Ethereum is more flawed and much less secure than Bitcoin.  Many predicted a year ago that ETH would overtake BTC in market cap but it never came that close and is a far cry from it today.   In the long-term I predict it is whichever coin is well adopted and works the best for the users and business but it is too soon and too hard to call in my opinion.

If we are talking about a secure, private, fast and easy to use coin with low fees that can be used as a replacement for your bank there are only a handful that are contenders and this is what our team is aiming for as well.