Well my predictions in ethereum is good but this questions is not possible because we all know that bitcoin is the greatest coin in the crypto, ethereum can be the second but not the first , it is not a threat to bitcoin,
Ethereum always a threat to Bitcoin, not only Ethereum, other altcoin also like that. Cryptocurrency is a field technology, value, function desision all. If a crypto cannot useful with community, they will delist it and use other crypto better than it.
I do not think that altcoins are the threats to bitcoin. They support each other and make the cryptocurrency world stronger and stronger. As you can see, bitcoin right now have the segwit, as same as the litecoin. In the future, bitcoin can also have the smart contract, just like ethereum