From some time now we knew about those models but now we have some sure informations from TENAA about them:
Redmi 4
System: Android 6.0.1;
Screen: 5″ 1080p;
SoC: MediaTek Helio P10 (?);
RAM: 3GB;
Storage: 32GB;
Cameras: 13/5MP;
Battery: 4000mAh.

Redmi Note 4
System: Android 6.0.1;
Screen: 5.5″ 1080p;
SoC: MediaTek Helio X20 (?);
RAM: 2/3GB;
Storage: 26/64GB;
Cameras: 13/5MP;
Battery: 4000/4100mAh;

processors are marked with “?” because Xiaomi made some twists with their clocks: Redmi 4 should have Snapdragon 625 but number of cores and clocks suggest Helio P10 and Redmi Note 4 should have Helio X20 but clock is lower.
Eventually This can be good and interesting propositions unless price will kill them of course.

Source: gsmManiaK (polish)