https://developer.blender.org/diffusion/B/history/particles_refactor/
And it’s really kicking into high gear now with the amount of commits today being way too many to count or sort through. All I know is that it currently includes support for new paged buffers and a massive load of general cleanup and refactoring.
I don’t know if it’s yet at the point where it can be tested or whether there’s already massive benefit on the user-end of things, but those who have been waiting for serious work on the particle system will be excited nonetheless. 