Right now, Node.js uses Google's V8 engine, the same one found in Chrome. Microsoft's recent pull request however gives developers the option to use ChakraCore instead. The comments stemming from the request are heated -- as you'd expect for such a change.
Incorporating Charka is no simple task, with the request altering a staggering 4786 files.
Chakra's principal PM manager, Gaurav Seth, goes into some detail about the decision on Microsoft's developer blog:
Whether the pull request will be accepted is -- literally -- open to debate, but going by the current comments over on Github, it will be integrated once it's been reviewed. Though, given the scope of the changes, it won't be soon.