The G-Class will also get a modern aluminum frame and drop roughly 800 pounds. Considering the G63 AMG currently weighs 5876 pounds that weight loss will be much appreciated. The locking differentials will remain so do not expect much if any of a compromise in off-road ability and start thinking the G is going soft.
The G-Wagon looks will be scaled down for a compact GLB-class. It will be smaller and cheaper and not as capable off the road. The X247 GLB will come as a 2019 model so it is not coming anytime soon. It also may be available as a front wheel drive as it will be using a variant of the GLA/CLA platform for its underpinnings. Scaled down G-Class looks but without any of the G-Class capability.
Expect more information to come as we see test mules over the next few years but the G-Class is finally getting a modern update. Depending on your perspective that is either a good thing or a bad thing.