One of the nice things about the Chakra engine is that Microsoft is moving it to open source. In fact, they announced in December that they would be moving the core components to open source, and now they have done so. This week Microsoft moved pieces of the ChakraCore to GitHub. This will allow the community (including you) to potentially participate in future development.
Chakra is currently targeted towards Windows 7 SP1 and above; however, now that it is open sourced, the expectation is that it will also begin to migrate onto other platforms. Microsoft has stated that they will be starting with Linux as the next platform.
You can find the roadmap for ChakraCore on GitHub at https://github.com/Microsoft/ChakraCore/wiki/Roadmap. You can also find comments from Gaurav Seth, Principal PM Manager for Chakra, at https://blogs.windows.com/msedgedev/2016/01/13/chakracore-now-open/