Big ones are a significant ProRender update and a nodal shading system. Stay tuned for the review coming soon for more.
Red Shift is a biased GPU renderer that's well respected for its speed and render quality. Red Shift is working on a realtime renderer based on game engine technology, and can use Nvidia's ray tracing hardware. Since there are some features not available with the Nvidia based renderer, RedShift lets the user decide based on their needs for a particular project.
Red Shift is available as a plug in for most of the high end 3D animation systems on the market, including Maya and Houdini, as well as obviously Cinema4D.
At NAB Maxon announced that it's acquired Red Shift, so going forward Red Shift will be part of Maxon umbrella, still under Nemetcshek.
Both are being very clear about a few things that will absolutely not change. One is that support for third-party animation systems will continue, using their plugin APIs. Two is that Red Shift pricing will also not change; it's going to continue to be a cost added option for Cinema4D as it is now.
What will change however is how Red Shift is integrated into Cinema4D; it will no longer be limited to using Maxon's plugin API, instead having direct access to the underlying code, so for those who have a Red Shift license, the integration will be transparent.