New Foveon is a long ways away still, they basically scraped what they had -

https://petapixel.com/2025/10/27/sigma-says-full-frame-foveo...

“But there are — to be honest, the project has been a little bit delayed… because every time we run the wafer and get the prototype sensor, we found some technical issues because we have never designed a sensor by ourselves."

This uses a partially-stacked bayer sensor, same as that in the Nikon Z6III and Panasonic S1 II (most likely, or very close to it).