Im not gonna lie here I do miss skiing on the slopes, and I do miss having fortwars in the sahara desert, but the shadows and shaders (even though it removes terrain) has a high advantage over the old system mostly because blockland runs smoother for me, and the day cycle is just plain amazing. I have been wanting a day/night cycle in Blockland since forever and now that it has one by default my mind has simply been blown.
Long story short, yes I miss terrain but I find the newer system to be much better.
If terrains DO manage to come back in the future I am almost positive the maps will be out of brick-style terrain and not torques default terrain system.
Also, I have a copy of Blockland v19 so if I ever want to play with terrains I can do so