the XCP dev's spot to a reporter and it was leaked out that they plan to push out Ethereum on BTC mainnet later this year.

So whether it is rootstock or XCP, there will be a few choices for using Ethereum smart contracts with BTC.

Btw when the premature news came out XCP went 3X within 15 minutes, then back down as the developers came out saying that the reporter shouldn't have put out the news as they still need to do more testing before they release it for BTC mainnet.