From the blog, the most important line:
This is by no means a full reimplementation. As the blog post tells us a bit later on
Eventually I’ll get around to update to whatever lies in the future. While we wait for Cycles X to reach completion and maturity, in the near future you’ll see an update to the latest full Cycles implementation.
edit:
Checking the technical presentation there are still a lot of open questions to be answered.
It is also to be noted that the blog post mentions deprecation of the OpenCL kernels in Cycles, meaning that there is no support for AMD GPUs until a replacement technology is utilized.
That all said, the numbers look promising for rendering on Nvidia hardware.