Hi, unfortunately i wasn’t able to finish it for 4.18, so it will be in 4.19.
As for details i can share, all i can say is that the bigger the landscape (i.e 255x255x2) the better the improvement, and i’m talking in the range of A LOT better 
It wont be simply a shadow fix, it’s a big refactor of the whole rendering code for landscape, changing how some stuff is calculated to give better LOD distribution while having better performance. Which mean that mountains at far range will have better LOD than flat terrain at the same distance.
Anyway, i’m close to be finished, and to give an example of improvement, i’m using LandscapeMountains sample as a test project and i resample it to different landscape size based on my test. If i’m using tessellation with a factor of 3 in a 255x255x2 map with a big view of most of the landscape (light in the back to have the worst case for shadow), before it was around 9-10 fps on a GTX 1060, right now i’m closer to 30-40 and i’m also seeing improvement on PS4, not as much, but there is improvement
Also there will bit a lot more info in stat landscape and property on the landscape actor to tweaks to achieve what is desired so perf improvement could be even more or less depending on the settings you will uses, but the default one will be tweaked for better visual and better performance.
Hope you guys will like it 