Ethereum is less scalable than Bitcoin.  There's hardly any users in Ethereum (only speculators) and the blockchain has bloated to many gigabytes.  There's also credible security concerns about the whole Ethereum technology after DAO.

Realistically, the 'old money' of Bitcoin will probably move over to the twin Litecoin.

There really isn't a viable "let's steal Bitcoin's userbase" strategy for alternates.  You have to go blue ocean and gain adoption from people who are not already in crypto.