Ideas based off outside commercial products would require a process LEGO might not be able to settle, especially Minecraft. Sure, they promoted that video at Minecon where the guy showed Minecraft as LEGOs, but would it really be so straightforward? Real world construction toys are not cubic units like in Minecraft. Conversion would be difficult, and overall point would be lost. You'd either be following strict guidelines, losing the creativity aspect, or out on your own with only the basic instructions that give no aid to finding the amusement of a more difficult, more easily frustrating version of something you could play on a computer without such hassles as losing bricks forever.