This rumor is coming from the Chinese forum Xitek, so take it with a grain of salt:
"According to news from Japan, SIGMA's full-frame X3 SLR camera is indeed coming soon. The new full-frame X3 chip is surprisingly three-layer photosensitive RGB, not 4: 1: 1! The new model is named SDQF. The fastest time to market is the summer of 2020. According to data released by current internal mysterious characters. It ’s still the old SDQ model, but it has purchased a more advanced focusing method. Free point focus can be extended, the peak focus display is clearer and more accurate, but there is no development plan for eye control focus. Full-frame mirrorless series DP1F, DP2F will be delayed for two to three months,.The DP3F and DP0F have technical difficulties and have not been resolved."
I think the "SLR" translation is wrong - this rumor is most likely for the upcoming Sigma full-frame mirrorless camera with L-mount and 60MP Foveon sensor with X3 1:1:1 technology that has been a part of the Sigma L-mount lens roadmap and it was confirmed to be announced in 2020.
