It's also related to efforts in Xbox, HoloLens, Surface Hub, IoT, and even still relevant to Windows on phone handsets despite no indication that that is currently a main goal.

The goal has appeared to be since Windows 8 to have a modular Windows where you opt-in/buy-in to legacy backwards compatible systems as needs and hardware change. Polaris isn't so much a new idea as the next in a series of codenames for efforts that have been going on for some time.