For tech geeks, the initial steps for the theme project are:
- Converting the less from bootstrapbase to sass and combining it with the sass from bootstrap4
- Adding renderers and templates, removing custom CSS rules and updating the markup to directly use bootstrap4 classes
- Integrating a sass compiler in moodle so we can re-compile the theme when settings are changed
- Support for an auto-css flipper for RTL
So, if you are also a Moodle theme designer, then you can share your ideas for the New theme project in this Moodle forum thread.