Some of the limitations are architectural, and as much as we would like it to be future-proof, some things will always be a compromise that had to be taken in order to be able to run it on the current hardware. In other words, it's not quite possible to make it completely scalable into the future, when you have to implement some optimizations that make it run on the current hardware, but also place some constraints on the tech.
However, even with the current implementation, the grass has a potential to cover larger areas than it does now. The distance limit should actually depend on the terrain quality and FOV setting, not to be a fixed distance.
50m is for 480p quality due to the fact that the terrain level to which the grass rendering is coupled covers slightly above 50m distance with default FOV. However, with twice as much the quality it should be able to go farther (but not twice as far because of the perspective though). At the moment the grass is cut after 50m regardless of the quality setting, which is wrong and will be fixed. The distance will then depend on the terrain quality setting, which I think can go further than 1080p even now but you have to manually edit the world.cfg. However, at the moment the settings don't adjust properly when you change the quality and even 1080p is problematic and needs additional tweaking of terrain cache size.
Once fixed, it should allow you to extend it all much further, provided you have enough GPU memory available.
