I've always wanted to see Minecraft programmed in C, instead of Java, and yes, with much milti-threaded support. SDL2 and OpenGL would be great platforms to program Minecraft in. I wonder just how efficient Minecraft really even is.
If terrain is generated by an algorithm, and the "surface area" of large lumps or deep layers of materials is less than 1/4 the total volume of blocks by a large amount, memory can be drastically reduced and performance boosted. Why less than 1/4th? Because if you load every individual block, all you need is to load and store the block id's in an exact order, but if you load the surface area of materials, you need a block id, and three values for 3D coordinates for every block.
This may all ready be the case, but I don't really know. Being programmed in SDL2 would be great though. I support multi-threaded Minecraft.