Google appears to be working on a new operating system codenamed Fuchsia. The operating system seems to be written from scratch and targets different platforms like mobile and PC.
Phoronix writes that the new OS is powered by what they call the Magenta and LK kernels.
The documentation mentions:
"LK is a Kernel designed for small systems typically used in embedded applications. It is good alternative to commercial offerings like FreeRTOS or ThreadX. Such systems often have a very limited amount of ram, a fixed set of peripherals and a bounded set of tasks.
On the other hand, Magenta targets modern phones and modern personal computers with fast processors, non-trivial amounts of ram with arbitrary peripherals doing open ended computation."
Google hasn't formally announced this new OS yet but several git repositories have appeared online here.