I checked the spec earlier and it’s impossible to make it backwards compatible with Sass without some slight edits, at least according to their GH issue on it. It’s worth watching though I suspect <style type=“text/scss”> or something like it will be added before we see broad adoption! :)
Possibly. I think the extra `&`s are something that could wash out with one-time tooling, and that the desire for `@nest .parent &` would bump the conversion rate, but it's always fun to watch the comings and going of standards.