Since then, XDA Developers managed to confirm that Alt OS refers to Windows 10 and that this project is intended for public release. Project Campfire aims to make a dual-boot Windows 10 system seamless, but the downside is that you'll reportedly need at least 40GB of storage. The site predicts we may hear about Project Campfire at Google's upcoming hardware event:
Campfire and Alt OS mode are visibly incomplete at this stage with no UI changes to speak of. However, the developers have been pushing fairly hard to get changes merged sooner rather than later, indicating a tight timescale on Chrome’s roadmap. Google’s hardware event is just around the corner, with rumours of a Google Pixelbook v2 featuring alongside the heavily leaked Google Pixel 3 and Google Pixel 3 XL. It would be reasonable to expect an announcement or demo at this event, even if the full functionality isn’t ready yet.