When Ethereum finally becomes the biggest blockchain by market cap 0xBTC will become the BTC emulation that is used as a deflationary store of value on that blockchain.
Bitcoin will die and cease to be a blockchain of any importance and people will switch to investing in 0xBTC which is compatible with the Ethereum network.
I cannot see this happening. Bitcoin is #1 not because it's the best technology. It's number 1 because its trusted and its first. Whatever is going to beat Bitcoin is also going to crush Ethereum in the process. I think the only thing that will take down Bitcoin is an incredible advancement until then Bitcoin is still #1