@Altimor: Never mind, I also spell german words wrong too, like "Projekt" with c
To the Tesselation: Yes just adding tesselation to the maps would end in a mess with..running into slopes or walking in the air.. If you would just add a bit tesselation like 10x and not 10.000x, It will be still low res enough to load the mesh, as static, to the cpu and generate a correct collision detection.
Here is also a solution for real time collision of heavy tesselated objects with voxelization:
http://research.microsoft.com/en-us/um/people/cloop/collision.pdf
plan b) Using parallax occlusion mapping to just add more detail, like flat 3 structures.. stones, dirt + grass shader to hide the low poly terrain.
Q: Is it possible to get the terrain, mesh more hi-res (tighter mesh)? I wouldn't affect older maps, but new maps could be made with more detail and hi-res highmaps.
sorry you triggered me with what you said about still low-poly terrain, and now I cant sleep anymore ;D