There are some good news. YAML 5 will be available soon as beta and this new version implements some important features required for Drupal 8. The Drupal code still need to be written, but until Drupal core 8 is going to be released it may be half a year or more left.
Many thanks to Dirk Jesse who has made it now possible to generate the YAML CSS files in YAML 5 with [dir="rtl"] what makes it possible to use RTL in Drupal 8 the native way.
If you are interrested to get this upgrade done sooner than later this project needs Your help. This is not a question of covering the full costs this port requires. Every donation will help moving the project forward. Please use below Paypal donation button for sponsoring the port.