I’d recommend not moving the data until a few issues are resolved:
Identify the staff person that owns the mdn/data repo
Determine a versioning scheme and release schedule for the NPM package
Convert existing macros using the mdn/data data to use the NPM package
Fix translations in the kumascript repo
I doubt these issues will be resolved in the next six months, and the resolution may be to retire the mdn/data repo. Until then SVGData.json in the kumascript repo is a good home for the data.
I initially created the CSS data in the mdn/data repo scraping the page contents, like I did for the SVG data in mdn/kumascript/macros, though I didn’t work on them for a long time. So, I wouldn’t call myself the owner of mdn/data, but I’m happy to help with the migration.
I agree with John. Though I believe that if work on this is focused, it can be done in a shorter time frame than six months.
I’m also wondering how we handle l10n nowadays. For your information, when I did the initial parsing, I simply scraped the translations from all language pages and matched them as good as possible to the English version. And I was forced to split the translations between {{SVGData}} and {{L10n-SVG}}, because there was a length limit for macros.